The home button on my iPhone wasn't 100% dead yet but it would intermittently stop responding. I had learned to live with the deficient home button but was gifting the phone to one of my kids and knew I'd never hear the end of it!
The overall process went very well... it was a little scary at times that I was going to lose one of the tiny screws or maybe rip one of the delicate ribbon cables. After all was stuffed back inside with NO extra parts except for the 'bad' home button... I fired it up and was greeted with the familiar White Apple! I functionally tested everything and it all seemed to work as it did when it was brand new!!!
The screws are TINY and DIFFERENT sizes... be sure to keep them marked some how... I laid out everything on a piece of cardboard as I took it off the phone and used colored markers to mark the color of the screws based on the color dots on the instructions. It worked perfectly!!!
Phillips #00 Screwdriver
Flathead 3/32" or 2.5 mm Screwdriver
SIM Card Eject Tool
P2 Pentalobe Screwdriver iPhone
iPhone 4 Home Button Assembly