Maybe you should compromise. Pay the friend a little under the table to repair your truck. I have done just that.
One of my friends had a degree in car repairing, and he was working in an auto factory. He charges friends $20 per hour instead of the $50 per hour "normal rate" out there. It is under the table. So there is no tax and he get to keep 100% of the pay. Without doing it for free, the jobs are always get done on time. We pay less than we should have been charged.
We pay less than we should have been charged.
