A few things about this
#1 yes he can take you to court and sue you for slandering his business esp with advertising on the net. Same reason why the newspaper wouldn't let you put something like that in their classifieds, they don't want to be involved in a law suit they know they will lose. Just talking about it on here is nbd slander that b*tch as much as you want, but when you put it in business advertisements its a whole new ball game, people don't understand that. Try to understand that his reason of going to court and your reason are two different things, and it blows but he is in the right just as much as you are (probably more since he owns the business)
#2If nothing was in writing, the verbal contract is null after payment or after very short amount of time, you have to find out specifics with an attorney. I would not go to court, I promise you will not like the end results of that case. I know hindsight is 20/20 but if I ever pay for anything car-related for over 300$ if not from a company with returns/warranties etc I get a receipt in writing with the item, condition, date, person, signature, and a third person. AND a date where the seller agrees the verbal warranty is effective to. For example, if I buy a used transmission I will get him to write down this transmission is in x condition if not he will give a full refund, and uphold that statement until x date. That way when you get the 600$ transmission installed a few weeks later and its broken, ask him for money back if he doesn't then tell him you must sue for your money back if that doesn't get him to cough it up, file suit before x date. This same logic can be applied to body shops and mechanics (body shops may have some clause in their business contracts that protects against something like this). Small business mechanics are usually very vulnerable to this type of thing but it must be in writing or its just no good. Doesn't matter what he took, broke, stole, fixed or didnt fix, its not in writing, it didn't happen.