My 80 GB iPod Classic battery finally gave up the ghost after 9 years of continuous use. I contacted Apple for a battery replacement quote, and after I stopped laughing I called a local independent shop specializing in Apple products. They informed me that the iPod classics were one of the few devices that they would not touch because of the risk involved. I found iFixit online and ordered the battery kit and an extra spudger. The kit arrived in short order.
I watched a couple of videos on the iFixit site and had the device open and un-damaged in about 5 minutes. The battery was stuck with double stick tape which was the hardest part... I didn't want to tear the ribbon cable wires beneath it. A minute of careful prying and the old battery came free. I had the device reassembled in 3 minutes without any problems. The first thing I did was check to see if it worked... and it did. I charged the battery overnight and have not had to charge it since. I've used it for three hours straight on music and a half hour on video. The battery still shows over 3/4 charge. It used to last less than 10 minutes. I am very pleased with the quality of the product, the tools supplied with the kit and most of all, the excellent tutorial videos provided by iFixit. The videos convinced me that I could do it myself after Apple's ridiculous quote and the repair shop's refusal to touch the iPod. This is a very good value and a high quality product. I liked it so much I bought another battery to repair my wife's iPod.
Use the iFixit website to correctly identify your device. Watch the iFixit videos before purchasing the product. If you can follow the directions in the video and are comfortable using the tools order the kit When the product arrives re-watch the videos before and as you work. Follow the advice that you get from the videos and take your time. It is not as hard as you think it is.