It's sad that the iPod is what resurrected Apple from the grave. For the money, the iPod is a rip-off, unfortunately I found that out the hard way. I personally cannot wait for more advanced mp3 players, hopefully from different companys, that allow you to store songs without being dependant on iTunes libraries and what have you.
Anyway to answer your question, I'm almost certain you have to pay perhaps more than you payed for the iPod itself to replace the battery. Yeah, it's a pain. Once you **** up the battery, you're pretty much f*cked.