I took my Sonic in to the dealership to have the compass fixed (it showed "--" instead of a direction), and they updated the software on the car. The update corrupted my radio as I've read others have had issue with, and now it isn't working at all. Sometimes the screen will turn on as far as the "mylink" startup screen, but that's as far as it ever gets. I've tried leaving the car off for a while, replacing the radio's fuse, and a few other things, but I'm all out of ideas. The dealership never made any record of having done their "repair," are refusing to correct the mistake, and are now quoting me about $500 to have the entire infotainment system ripped out and replaced.

Do I have any easier options to try first? Would it be potentially cheaper to go to a different dealership or an independent repair service?
Thanks folks, I'm getting pretty tired of driving in silence.