I'm taking my challenger in to do it's 20,000 miles scheduled maintenance soon and I was just wondering if someone could give me a rough estimate of how much it's going to cost me. Also, is it possible to take it in a little earlier than reaching 20,000 miles, or would it be better to wait until then? I'm at about 18,500 but need to change the oil already so wanted to kill two birds with one stone.