I ran into a tree, the front of the car was.

I ran into a tree, the front of the car was totaled, took it in for a diagnose to a mechanic, he said that 'this' will fix it, asked $6000, so said okay. After 3 weeks, which he has told us that the parts take a while to get here, after 'this' has been fixed, he says that there's a problem with the engine and that the car will not operate. He still demands his $6000. Should I pay him?