Yes it is a good idea to know what your insurance agent will do when the worst happens.
Basically it 'should' work like this. You bought a contract with your insurance agent that if your truck is destroyed in a collision, it will get replaced. They should be replacing it with a like year and like condition, so not a truck that had the frame untwisted and a cheap paint job, but a truck that had not been in a accident before, with similar mileage. One insurance company claims on the commercials that they will replace your totalled car with one that is a model year newer and about 15,000 less miles on it. That is 'Making it like it never happened'.
Now your insurance agent has a signed contract with you to replace your truck should it get damaged during the next 6 or 12 months. They will own the wrecked truck, and try to sell it and recoup some money. The engine, transmission, and 3 tons of steel are still valuable. IF the damage was due to the mechanic, they will go after that company to recover their loss. You do not need to worry if that insurance company will cover the loss of your insurance company.
In the case of a drunk driver, they probably will also go after that guy as well. And a insurance company can 'step away' from covering certain things in the case that you operated the vehicle while drunk, but still needs to cover a un-authorized driver who might have driven it drunk.
I did see pictures posted - taken by a guy who was driving past a RV repair place. It was a RV that had slid off the lift, and one of the jacks was sticking through the sidewall of the RV. It looked pretty bad.
Good luck!
Fred.