10 - 20 Minuten
My wife's laptop had a tragic encounter with some spilled wine. I used iFixit guides to strip down and clean the entire machine, but the innermost layers of the keyboard are permanently sealed and I couldn't get most of the keys working again no matter how clean they looked.
The repair was smooth and easy. I'd removed to upper case once before during the cleaning, so the later removal and replacement only took about 15 minutes from battery out to battery in.
To keep track of all the screws involved in this repair, I drew a quick sketch of the bottom of the MacBook and taped each screw to the drawing in the place I got it from. This kept all the screws from rolling away and told me precisely where to put them back.