1 - 2 horas
No response from power button. A kid dropped my phone and the power button quit working
It is difficult. Give yourself a couple of hours. Organize all the screws as you go, as there are about 15 removed. Definitely use the magnetic screwdriver.
When removing the earpiece speaker, pay careful attention to it's orientation. It is stuc on with adhesive, but when you put it back it it can go in a number of ways. I got lucky and figured it out by the way the adhesive pulled apart. It doesn't have a snap in attachment point and my speaker looked different than the photo. Also, the last screw is tough as you can't go at it straight on- a connector blocks the correct angle, so be carefully not to strip the right power cable sensor screw. Also I lost a bit of foam off one connector and the connector cover wouldn't quit snap back down, but it worked.
SIM Card Eject Tool
iPhone 4 (GSM/AT&T) Power and Sensor Cable
iPhone 4/4S Liberation Kit