I'm not going to shop around for car repairs when someone else is paying for it
Usually, car repairs are cheaper if you shop around. Why won't you do that?
I was once ripped off by a car part shop, so now I'm too worried to go there.
Normally it's your own responsibility to pay for your car repairs, but if others are willing to help you, you should at least shop around to help them out in return.
I want my car repaired for free.
It would be great if we could get our cars repaired for free, but the truth is that it is a hard job and requires a lot of specialized parts, so it is expensive even for honest mechanics.  Since a good mechanic will save you a lot of time and trouble, as well as money, you owe it to yourself and to your benefactor to find the best garage.