Well, since I don't know of any site that has a used value for the C's yet, my advice would be to go to the dealer you bought it from, explain your situation, and ask them what they would sell it for if they had a used one with 4000 miles. Just tell them you aren't interested in trading it in to them, you just need to get an idea of how much to ask for it. I would think that the used car manager would be able to give you a rough idea given your situation. Contrary to what seems to be said all the time, not all dealerships are crooks.
I would say about 4,000 less than you bought it for, but I really have no clue, and I've read here and elsewhere that Chrysler's resale value is pretty bad. Don't know if that would apply to such an in demand car though.
Good luck!