Currently Being ModeratedDec 18, 2012 9:44 AM (in response to BFDIII)
I've had good luck using iFixit. They have great instructions for repairing all kinds of devices, esp. Apple computers and iPods/Phones. They sell parts, too. I just installed their replacement battery for the iPod 4G/Photo, and everything appears to have gone well. I checked, and they have instructions fro the 5G, too. Here is the link to their instructions.
They do sell replacement batteries for 30 Gb or 60/80 Gb models for $15 right now. I've seen some cheaper prices (on Overstock for the 4G battery), but don't mind supporting the folks who provide the instructions. And I trust their advice and products.