GM has done a real good job of tying you to the dealer for this repair. They refused to allow us to buy radio service manuals since the '94 model year so you're tied to their grossly over-priced repair centers. Beginning with the 2002 models, to prevent you from buying a high-quality aftermarket replacement radio, they began building the Body Computer into it. Without that radio, you won't have cruise control, power windows, and many other functions. It is also the master computer that sends out signals to turn on all of the other unnecessary, unreliable computers when you turn on the ignition switch.
Once the radio is repaired, it must be installed and programmed to the truck by the dealer. The typical cost by the time you're done is around $450.00. That nonsense is just one of the many reasons I'll never buy another General Motors vehicle. They don't care though. For every lost customer like me, they will make a lot more money from the "got'chas" from other unsuspecting owners.