Reputable car dealers have a book published by the manufacturer on the
amount of labor to repair something in the car. Sometimes it takes
less time, others a bit more time depending on the mechanic. But the
shop will charge the book rate either way.

[Dad used to be a fleet manager for Ford and I've spent waaaay too
much time hanging around]

Unfortunately the shop rate these days (at least in Colorado) at the
dealers is $90-100 an hour. The aircraft shop I use is $55/hr and they
provide a really good estimate before they do any work.