Legal Question in Legal Ethics in Illinois

Depends what your deal was. Sounds like there was more, something like you agreed to pay $X if the seller had certain things done, and it now cost the seller more. So the seller has your money, used it to pay for the repairs, and is coming up short on his bottom line net of repairs. If you have nothing in writing, it will be difficult to prove what the deal was unless you have witnesses. And it costs money and time to sue, so you may want to work something out with the seller since the car must now be repaired and ready to be sold to you.