1 - 2 часы
My lovely wife dropped her iPhone 5 in the sink while the faucet was open and eventually the loud speaker stopped working. The battery was not lasting long either. We try to buy a refurbished unit at Apple but they did not have them.
I used iFixit's step by step guidance and watched the youtube video a couple of times. Everything went well with no complications. The hardest step for me was pulling the battery. I had to be careful when rotating the logic board to not damage the camera flash. Also I had to be very careful when removing the loud speaker assembly because is glued to the case.
I adopted the concept of the magnetic pad you show on the video. I printed a large picture of the iPhone internals on a letter size paper. Then I placed the printout on top of large picture fridge magnets. As I removed the screws and parts, I placed them on the corresponding location in the picture. It helped a lot to keep things organized.
I would update the last step of the instructions to mention that the "ribbon looking" part with two washers and glued to the loud speaker has to be removed and placed on the new unit.