1 - 3 uren
After a soap spill on my keyboard, many keys did not work normally even after several days. I did not remove the black cover on the back side of the keyboard however, since it was glued onto it and I was afraid of just ripping it off. In hindsight it's possible that disassembling the keyboard completely would have helped, I will keep the old keyboard around and perhaps try that one day.
Replacing the upper case is the hardest repair I've ever done, but most of the process was straight-forward following the guide from ifixit. I guess it took two or three hours. Using the 54 bit driver kit from ifixit, I had problems with two PH00 screws getting quite stripped (loosing their shape) – making me quite frantic since there are no extra screws. Luckily I had another PH00 screwdriver around that eventually helped me getting the now-quite-damaged screws out. Advice is: be very careful not to damage the screws :)
Overall, I found re-attaching the keyboard cable the hardest part. It's too small to get a grip on and since it's all flexible it's just very hard to find a way to apply force to it. I tried over and over again many times before I got it. I used a combination of plastic sticks to align it and apply force from below, and a finger to apply force from above. After aligning it, I first pushed it in slightly on one side, then the other side, repeating this a few times. It's hard to explain of course.
There are lots of different screws, so keeping track of them is important. I just spread them out on a large table and added post-it notes next to each group of screws.
I was also a bit worried about loosing track of the order of the three antenna cables. Luckily I found that I really did not have to detach those. You can keep them connected to the little wireless module during the whole repair. Similarly, there is really no need to detach the fan connector, which is somewhat hard to get off.
Before disconnecting the keyboard cable, take note on how far into the connector the cable goes. Since there's no "click", it's a bit hard to know when re-attaching it afterwards.
Oh, and don't forget that when you order a upper case replacement from ifixit, you get the US keyboard layout. It's obvious, but still I didn't think of it :)