Jumper cables incorrectly used

Hi, I read through the post regarding the Jeep that was jumped incorrectly. But, I was wondering if you could give me the specifics on potential damage to my car? The cables were only on for about twenty seconds and when they were corrected, the car started immediately. I tested lights, blinkers, air, which were all working, but the radio is not working.

I am going to take it to my mechanic, but I would like to know what he should be testing and looking at. I am assuming fuses, but could the alternator potentially be damaged? What other damage could be lurking beneath the surface? As well, is there a fix for the radio beyond replacing the entire thing?

While that issue is result of utter stupidity, the battery was run down because there is a fan in the motor that is not shutting down even when the car is off. Can you speculate what that could be and how much it will cost to fix?

Thanks very much for your help.