Silly question perhaps, but can you not just ask them to talk you through the process in detail? You can them compare how they describe what they will do against the procedure(s) that other people you're considering would follow.
I guess my initial thought was that you may get the original quote down a couple of hours by questioning it. But yes there appears to be a substantial difference in time.
I'd add that I couldn't strip my window motors despite my best efforts and ended up replacing them with MB parts which were not cheap either.