According to what Wraith said they needed the car for two days which makes one assume that it's at least a 10-12 hour job given th fact that labor rates around LA are $70 an hour and for 1k that would be about 12.5 hours.
Thing is the job could be done quicker but flat rate is how mechanics make money The rate book says flat rate is 5 hours at say $70 an hour.
So the mechanic tells the customer that it will be $350 for the work and then does it in 2-3 hours or less.
Unless something unforseeble happens at which point he calls the customer and tells them it's worse and it's going to cost extra. Lol that's how it works.