Billy, have you tried resetting the mp3? There should be a small hole that you can insert a paperclip into, and the device should reboot. If you tell me the make/model, I might be of more help. The GeekSquad is highly overrated...
That being said, if the thing is truly dead, you should go with something that your budget approves of. Satellite radio is cool, but expensive for monthly service. I don't generally advocate iPods because they're hugely overpriced, but if you love Apple, the iPod simply works and is good for those who have already committed to iTunes/Mac.
For me, I like my generic mp3 players. Right now I have a Creative Zen that I bought refurbished. When it dies, I'll probably go with one of the Samsung or other small, portable players. Cheap and simple are the things I want from my single function gizmos.
You can buy a player-to-car adaptor for nearly any player on the market. So the big questions are: What do you want it to do? And how much are you willing to pay?