RE: Price for a decent old one? (vs. new)
I would say the type of Challenger you are looking for is going to be between 20-30K. You can find some cheaper, but may require some or alot of work.
Pick up a deals on wheels or round up magazines at the store, and they offer numerous of cars for sale. That's what I used to look at before the whole ebay thing.
If you don't want to work on the car, I would recommend waiting for the new one when it comes out. If not, it doesn't require too much skill to be able to work on cars. The main thing is to do your research and be prepared to work on the car all day. There's a lot of things I don't have a clue on how to repair, but I'm willing to figure it out.