My iPhone 3G's battery was useless
The repair went very smoothly with the online guides and the parts/tools. I ordered all the necessary tools recommended on the site and that really helped a lot. I was able to change the battery all-in-all in about 30 minutes. You have to be delicate and the guides really give you this advice on the specific parts.
None. The guides and the tools/parts were perfect!
iPhone 3G Replacement Battery
Phillips #00 Screwdriver