I agree, we had an '86 vette and when a called over to Nahas service they could not even answer some basic questions and were definitely not interested in servicing the vehicle. i was eventually able to find the answer and make the fix myself.

I had the same response for a problem with my 2003 vette. I wanted them to turn off a function in the car's computer that won't cause any safety or drivability problems. The service writer went in the shop to speak to a mechanic who told him he had never done that before. I came back the next day with a printout showing step by step instructions and pictures on how to do it with the Tech 2 scanner. A 5th grader could do it. not difficult at all.
Service writer said they would get back to me, that was over two weeks ago. and still no contact from him. I probably should have printed the pictures in color instead of black and white.

I took a chance and bought a Chinese clone of the GM Tech 2 scanner on line and did the job myself in less than 15 minutes which included hooking it up and disconnecting it.

I had planned on using the dealer to perform services on my vette but wrote them off my list. If their mechanic isn't smart enough to follow simple instructions I don't want them near my car.