Resolution
UPDATE: (this turned into longer than I expected - I apologize)
Hopefully this will help somebody else out there. I wanted to pass along what I learned, my mistakes, and my ultimate success in resolving this issue.
I have a 2011 RT Classic that I've owned since Feb 2012 (51k miles). In all that time I have babied the car even though I have no garage and it stays in the driveway (daily driver from 2/12 to 2/14; spends most time under a cover 2/14 to now). I have always taken it to the dealership to have all work done as I have a pretty good dealership nearby and figured they knew more about it than I do. Finally decided to do some stuff myself, learn something, and save a few bucks.
Several weeks ago I took the car to take my boys to their basketball practice. It's dark and I immediately notice that something is wrong with my gauge cluster. At first I think it's water damage as the bottom half of the gauges is darker, but it's not straight across -- it looks like water wicking upwards. I decide I'm finally selling the car. That's it - done with it! I love this car, but this car has literally been in the shop more times than all of my other cars (and all of my wife's since we've been married (going on 19 years) combined. Seriously. That's the truth. Still love the car. After I calmed myself I turned to the internet to see what's going on and how much it's going to cost me to fix it.
THE PROBLEM: there is a white flexible illumination sheet behind the gauge faces. The illumination sheet gets it's power from the electronics board (lead just plugs into the board). Mine just started going bad. One day it was fine, the next time I drove the car it was not fine. I don't know how common of a problem this is.
OPTIONS: (out of warranty)
1) Live with it......I couldn't do that. I have always fixed everything on this car as quickly as I can. Cosmetically, mechanically, or otherwise. I wouldn't say my car is "mint" -- it's 7 years old and kept outside (under a nice cover), but I would say it's better than "very good". Cost -$0
2) Take it to the dealership. They pull the cluster out and send it off; they receive another cluster and it's installed after being programmed with your mileage, etc. They keep your car from start to finish. This is an expensive option, but I did consider it. Cost - around $800 - $1,000 (based on internet reports)
3) Fix it myself. Cost - around $80 - $500+. This repair can easily be done for less than $100. The only thing you have to buy is a used gauge cluster - they can be found online.
I went for #3. I started this thread asking about physical size of the cluster itself between the different models. In researching this issue I found that some people were buy aftermarket gauge faces and replacing the stock. This intrigued me, and I thought about changing my gauge faces, but ultimately chose to remain stock. This also intrigued me because while looking for used clusters I noticed that SXT clusters cost less than RT clusters. Around this time I also discovered that the illumination sheet can't easily be found by itself - I never found a source for one.
There are auctions online where you can buy a used cluster and programming. This works by removing your cluster mailing it to the seller, they program the cluster to match your original, send you the "new" one, and you reinstall it. Done. I quickly looked at this. This would have cost around $350-$400. Better than dealership cost, but still kind of expensive.
Kept researching and saw a guy that said he bought a used cluster and transplanted his electronics from his original cluster to the one he bought. I do not remember where I saw it nor the OP's name, but I stole his idea and I thank him for it. I doubted that I could pull this off, but in the end it wasn't a hard project.
I watched a lot of videos of people removing the gauge cluster - it's fairly easy, BUT do be careful removing the gauge cluster bezel. There are three places at top where the bezel clips clip into -- they are made from fairly thin plastic. Bad design - very least the plastic should be a little more heavy duty. I broke all three to varying degrees. **FIXED this by super gluing the plastic back together. Over a period of several days I built up super glue around the outside of the breaks being careful not to get any on the inside where the bezel clips in. I did this about 3 or 4 different times letting the glue sit for a day or longer between each time. At the end, I mixed up a little epoxy and applied around the outside of the breaks with a toothpick. From applying the epoxy to reinstalling the bezel was over a week. I doubted this repair would hold but it worked. I even had to remove the bezel once and then reinstall a 2nd time and that repair held. Watch different videos of people removing the cluster - spend the time to learn exactly how it's held together and be careful (I wasn't as careful as I could have been). It's not bad.
So, I found a super cheap SXT cluster for about $40 and bought it. I figured I could used my gauge face, lens, and electronics board since people were replacing the stock gauge faces. Couldn't be hard to swap the stock. WRONG. Never could make it happen. I guess the holes on the stock face are smaller than aftermarket gauge faces. I'm not saying it can't be done, I'm saying I couldn't do it. I couldn't return it since I had opened it and damaged it. I ate that $40
I order a 2nd cluster - this time from an RT. Got it in, plugged it into my car to verify that illumination worked correctly. Nope. It too had an illumination problem. No modifications to it at this point, so I returned it and got my money back.
I ordered a 3rd cluster and this time it passed the illumination test. I watched more videos of people swapping out their stock gauge faces -- watch those videos and you'll know exactly how to take the cluster apart. At one point you have to take the gauge needles off. Be easy, you're working on top of the illumination sheet so I don't think you want to put too much pressure on it. You can think of the gauge cluster as having 4 main parts - lens cover, gauge faces/illumination sheet on a plastic board, the electronics board, and the back cover. I only used the gauge faces/illumination sheet mounted to the plastic board from the purchased cluster. I reused my lens cover, electronics board, and back cover.
My total cost for this repair - $130. I could have done it for $90 had I not originally bought the SXT cluster. It was a learning experience and it was still a lot cheaper than having the dealer do it out-of-warranty.
BIG THANKS TO HAL H IN THIS THREAD -- he quickly answered when I had questions.
NOTES:
* Take lots of pictures of your gauge faces before you remove cluster from car. Car turned off, car in run mode, and car started. This will help you reset your needles right before you reinstall your repaired cluster later.
* Also mark where your needles are on the gauge face with a sharpie or something - always mark where it will be hidden by the lens cover.
* As you are removing your dash pieces and cluster, use a piece of cardboard to stick your screws in labeling each set as to what they go to. Saves time if you have a bad memory like me.
* SXT speedometer goes to 140, RT goes to 160, SRT8 goes to 180*
* 2008 to 2010 faces are the same, 2011 to 2013 faces are the same, 2014 is slightly different, and then in 2015 it changed again. I do not know the differences after 2015