20 - 30 minutos
3GS crashes 20+ times/day. Would not boot up unless plugged into a power source.
Pretty easy, but later determined my camera wasn't working.
Make sure when disassembling the circuit board, you also completely remove the camera and reattach it to the board, then reinstall board and camera together. This way you ensure the camera actually attaches to the board (it might feel like you attached the camera's connector, but you probably didn't).