shlishi,
If the halacha is unclear, it would make a difference, because of ?????? ?????. So if for example, you brought the mechanic to a ??? ???? about the rotors, and the mechanic claimed that normal procedure is to try cleaning the rotors as the preliminary measure, and you brought some sort of evidence otherwise and the ?????? were uncertain about his claim, had you paid, they wouldn’t obligate him to repay you, but OTOH, had you not yet paid, they wouldn’t obligate you to pay (although in reality they would probably insist on a ????).
I’m not sure how whether or not you have your car back would impact anything; there’s no question that it’s yours anyhow.