Radio/Nav Malfunction - causing other problems?
 

My 2008 Suburban has 50 (!) error codes - it all started with the radio coming in and out, and then dying. Black screen, no sound, no sound even on turn signal. Other issues like Park Assist signal on, despite it being off, etc. Per GM, Dealer wants to charge me $2000 to replace radio/nav - and then see what the problem is. Interestingly on my 2001 Tahoe the same thing happened but I have never fixed.

Questions:
1) Reputable place in Atlanta GA for a second opinion/more reasonable price?
2) Any experience with this? Afraid I replace the radio/nav to find out it is another big thing/expenditure
3) Are Chevy radios just crappy? Why happening to me twice?