Sounds like you need to move your music library off your iPod to your computer. Try downloading one of the programs off of VersionTracker that allow this, like iPodtoiTunes. There's lots of options, and any of them might be good. The other option would require some work in the Terminal, as the folder that contains your music is hidden. I'll post that if you like, after I test it on my iPod. 😀
JW