How to I file a claim against my mechanic

Small claims in New York must be under $6,000 I believe.  If it is over that amount, you will have to start the action in the next highest court (if NYC that would be the Civil Court of whatever NYC borough; if outside the City, probably in the District Court of whatever county)..Whichever court you decide to file in, the website for that court will give you instrucitons about how to proceed, and if you have any questions, the clerk of that court can help you.