I am an electronics
engineer by trade I am not comfortable paying $80.00 to have a $3.00 part
replaced but way better than paying $1,800 for a new audio panel.

You will save most in airplane ownership if you do initial
troubleshooting yourself. Avionics and A&P shops make most money by
quickly turning around customers, unfortunatelly this is best done by
shot-gun parts swapping as opposed to systematic troubleshooting. Most
people say they want the latter approach, but in the end are not
willing to pay for the time, so its easier to just order a new part,
mark it up a bit, charge for couple hours of labor and you are out the
door. I couldn't afford to own an airplane in such hands-off mode, so
I try to diagnose problems myself, then steer the shop in the general
direction. (Of course there are things I simply don't understand and
have to rely on someone else's expertise, like major engine work, for
example).
Electrical problems can be pesky and beware that most A&Ps don't have
the patience to diagnose them correctly. As an EE, you are probably
more qualified on those types of repairs. It is important to use the
correct mil-spec materials however (wire, terminals, breakers, etc),
if only for the sake of resale condition.

Finally, aviation maintenance on small GA airplanes is not rocket
science, so "Never assume nefarious intent when simple incompetence
suffices as an explanation". (saw this great sig somewhere, author
unknown). Couple bizjets parked in the hangar are not a guarantee of
perfect work either (they do however guarantee higher bill :-)

Good luck, sounds like you have the right overall attitude, you are
right its a learning process. Annuals are another topic I could say "I
learned about flying from that", but that's another discussion...