Thank you for the question Dave.
In many cases dealerships overcharge and under service. The industry often charge for incomplete servicing. I have been on the floor of the workshop in dealerships many times in the last 3 years when servicing their workshop equipment.
I have personally witnessed mechanics in dealerships tick off service items without even looking, as they feel pretty sure it will not be noticed between services and they cannot stay within the alloted time for a complete service.
To a fare degree the same problem applies to privately owned service workshops.
The trick is to be able to tell at once if the workshop owner and mechanics are capable and have the intent of retaining the customer.
I provide the means of sorting out who is who in my hub titled How to save thousands on car maintenance. You need to look at attitude first. If the approach to you as a customer is professional this is also an indication.
I am fussy as hell with service as a motor engineer, because I understand what happens when all those bits rub together! (shudder!)
I like to get references from other customers for major rebuilds on transmissions and motors.
Turbo and high tech work is easier in a way as the industry has well known professionals.