2 - 3 horas
All of a sudden the power button stopped working. I ordered the cable and the button as a precaution as I didn't want to take the phone apart only to find out I didn't have the spare at hand.
Sadly, neither was needed :-(
All good except for the front camera. Leave it alone unless you truly have to replace the cable.
Be careful with the digitiser and display cable. They are right in the way of the power button and have a tendency to break.
Use a P#000 for the Philips screws instead of a P#00.
You need a flat screwdriver to remove the spacers. The bits that come with the iFixit toolkit are way too thick and the quality of the tools left me a bit unimpressed. Some are not up to the task. Make sure you have a thin flathead about 2.4mm at hand before cracking the phone open.
I ended up fixing the problem by carefully applying a few tiny drops of nail polish on the power button. The part that was needed (the actual power button switch) wasn't available from iFixit.
iPhone 4S Power and Sensor Cable
Magnetic Project Mat
iPhone 4 and 4S Power and Lock Button