lemmon car! help!?

i bought a 2004 dodge stratus, used " as is" no warranty, in house financing, bought on 3/29/08 broke down on 4/28/08, the mechanic said it was the timing belt and recommended get water pumps fixed, said that if that doesnt work it might be a valve...which is like $800....i can return car but ill loose down payment and first payment...is there any way that i can get my money back if i return car?

No. You are lucky that they are even letting you do that. If you bought it "as is" then it is just that. Once you signed the paperwork the car is yours for better or worse. Legally they don't have to do anything for you. I'm guessing since you did in-house financing that they would rather put you in another car and keep your original down payment and the first payment rather than have a default loan which they are assuming you will do.