2003 Benz electrical nightmare

We live in the middle of Illinois & brought our car to a Chicago repair shop to replace the radio with an updated radio, navigation & Bluetooth system. The radio never worked well, we brought it back for a better antenna. That didn’t help. It’s been 4 years now of no radio. We finally took it to our Benz dealer. Now there is no radio, no heat & no air bags. Every time Mercedes touches it, a different electrical problem happens.

Can anyone suggest someone who is good with Mercedes electronics? We will travel up to 200 miles to find someone.

Having similar problems with my '99 C280. No mechanic can fix it. Suddenly windows won’t work, dash lights come on for no known reason, etc. Believe it’s a problem with on-board computer. Trying to find dealer to reboot computer is hard, but this should be pursued. All offer varying excuses on why it won’t work, and need to buy new one & reprogram that. Too expensive! By all means, do not disconnect battery by yourself.