2 - 4 hours
My brother-in-law dropped his iPad 2, and it messed up the LCD. It still turned on, but never showed anything other than black. So I figured I could open it and see what was wrong.
In following the instructions to take off the screen, I got a little zealous and tore the Bluetooth/Wi-Fi Antenna. Oops. Always read ahead.
(The LCD fixed itself. I found a mysterious screw, which may have been shorting something.)
The repair went smoothly, except I didn't check every single cable/function before closing the iPad. I forgot to push the nearly invisible black SIM/Front cable completely closed.
So I reopened the iPad, taking care not to break the Wifi cable again. However, there was *absolutely* no warning about severing the lock button cable at the top left. Of course, that's what I did. At least it's a minor inconvenience.
1) Carefully read through the guide, taking note of any warnings.
2) Make sure you check all functionality before closing the iPad.
3) If you do need to re-open, don't be over confident and go slowly.