My iPhone 4 Home Button failed. I decided to try to do the fix myself, since Apple basically told me that they only recommend buying a new iPhone and don't replace defective home buttons on older iPhone's.
It went very well, thanks to the quality tools, and detailed instructions.
The many screws required to remove is daunting...they are so small! I highly recommend doing as I did...print off the detailed instructions, and tape each screw and part to the instruction page that they are associated with. This way you will not lose the screws/parts, and you will easily remember which screw goes where as you go back through the instructions to reassemble.
Phillips #00 Screwdriver
Flathead 3/32" or 2.5 mm Screwdriver
P2 Pentalobe Screwdriver iPhone
iPhone 4 Home Button Assembly