After falling in many adventures all over the world, my iPhone 4S screen finally gave up...
It was a perfect opportunity to looking inside and quite a challenge as you need to disassembly everything to get to change the screen (2h30 for the whole operation).
Everything went smoothly until I found an extra screw...but by chance, it was only from a few steps back.
The most stressful time was when I plugged it in and it would not work...but after 10 minutes it finally did boot up. Then it wasn't connecting to the cellular network. The fix was simply to update the date from 1970 to today, otherwise it would not read the SIM card. It is clever enough to know that SIM cards did not exist in the 70s. That's why we call then smartphones. Now it works perfectly !