45 minutes - 2 hours
The keyboard stopped working when water was spilled on it.
The repair shop wanted too much money so we just used an external keyboard. We finally found this an unacceptable solution.
We followed the iFixit instructions. The repair was almost flawless. The microphone connection to the I/O board broke when we tried to remove the wire. It is very fragile. Luckily, that is not a necessary feature for us. We didn't even test it, but it probably still works.
We put out white sheets of paper and numbered each step that removed screws or parts. We taped the parts to the paper with clear tape next to the step number. This was super useful for the tiny screws. We labeled screws when two different kinds were used in the same step.
We had to get a 000 phillips screw driver. We had 10 minutes to spare on New Years eve.
TR8 Torx Security Screwdriver
T5 Torx Screwdriver
P5 Pentalobe Screwdriver Retina MacBook Pro and Air
MacBook Air 13" (Mid 2012) Upper Case with Keyboard