[Ximpostrxx]

I have an ipod classic 120gb that I bought last summer new from apple... It's been working great until yesterday... I was in the subway and I went to turn my ipod on and when I did I found that all of my songs had magically erased themselves, it showed 0 songs, but in the about section it showed 30.4gb of space still occupied but that's impossible right? Because the ipod showed NO songs... So I called apple and I was taken through troubleshooting steps and put the ipod into disk mode in order to restore it (because it would freeze itunes everytime I plugged it in) after the restore I synced it and went to play a song on it and again it showed 0 songs and 30.4gb of space taken... Called apple back and the guy told me my ipod is out of warranty (I didn't get applecare [dumb I know but I have it on all of my other apple products]) So since apple frequently doesn't know what they're talking about I figured I'd ask you guys:
1)What's wrong with it and can I fix it myself???
2)I have an ipod video but the headphone jack is busted can I swap out the hard drives and logic boards if I can't fix the classic?

THANKS FOR READING AND SORRY I'M A LITTLE LONG-WINDED