I got screwed... What do I do?

I found a guy selling a car. I talked to him and took the car out a few times. I asked if there was anything that needed fixed soon. He told me the "motor mounts" were gone. I looked and sure enough one was missing. I bought it ($1200 merc. mystique) and took it to a mechanic i know. He called me and told me that it will take $750 just to make the car roadworthy. I paid in cash and I want the &^(^$% that sold me the car to help me out with some of the repairs bucause that is not a $1200 car! It will take at least $1200 to get it in fair condition.