Directfix.com recently posted a video on how to disassemble and repair an iPhone 3GS. If you are the fix-it type and you break your touch screen or you want to replace your battery or LCD…here are step-by-step instructions on how to do that! I honestly would never try this (Doug might) but, it is interesting to watch.
I also found that if you are willing to give it a shot, you can purchase the touch screen (IP-2320) and the LCD (IP-2321) for $69.99 each on their website. Below is the video demo.