Well for one... that would suck. That is probably the worst scenrio lol, but still you have to ask your self why you are thinking about doing it. If its is to help the person out (good samaritan award) then I wouldnt charge anything outside that persons budget. If it is to make some $$$ then I would call the local mech shop, ask how much they would charge, then charge half of that. I say half because you are not a licensed mech and I sure wouldnt pay someone one price when the mech shop only charges a little more with a guarentee/warranty. Hope this helps...