My iPod gets very warm. The battery holds for a while but not as long as
It use to hold. I've never changed a battery and don't know if I have one
That can be changed by me. Also, would it be lithium? That scares me.

I guess I could take to a town with Best Buy and pay for a Geek to
Change it, if that's the problem. Any advice would be welcome.

Brand and model would be required information, then you can watch how the battery is replaced, and get the costs on Google. Then you can decide if this is something you can do, or pay for a service to do it for you.

Unless you are highly mechanically inclined, I might recommend you get someone who does this frequently or for a living to do it. I've rebuilt an Ipod classic 160gig version a number of years ago that was found on the street damaged, literally in the middle of the street (I still have it) back when they were still THE thing to have. It's really very easy to damage it while taking it apart and all the parts and cables inside are VERY delicate.

New battery isn't very much, you could even order the part online and take it to one of those Kiosks in the Mall that repair phone screens to have them put it in for you fairly cheaply.