Neither my iPod 5g nor my son's iPhone 3g would hold their charge more than a few hours. I ordered replacement batteries for both devices.
The repair was straight forward. The repair kits were nicely packaged and provided all the necessary tools.The how to video on iFixit's site for the iPhone 3g was really helpful. It doesn't hurt that MJ is easy on the eyes ;-)
Keep the micro-screws from the iPod 5g in a safe, well-lit place.