Not really to be honest.
The B2's I have had dealings with apart from the odd one or two have always had a tendency to lie through thier teeth to get the aircraft out the door.
Most arn't truely independant and are tied to a service center for a brand.
And to be honest the service that I have seen with GA avionics in my neck of the woods is to be quite honest shocking. With usually more problems occuring after being tinkered with than before.
I would listen to an A&P with a pilots license but would always go and check with other pilots/owners before going with an avionics shop recommendation.
Don't worry its pretty common with instrumentation as a whole, boats are the same, and also A/D data acquisition in industry.