Dropped my Verizon iPhone 4 in water. Dried it out overnight and everything worked fine, but it wouldn't charge. Even used contact cleaner on dock connector.
Took maybe 10-15 minutes using the guide. Everything came apart and went back together smoothly (and with no extra pieces after!)
The rubber microphone "tube" is tricky to transfer from the old piece to the new one. Also a little difficult to put back in its metal housing.