2 - 3 hours
My MacBook Pro's upper case didn't look to good, after it fell like 1 meter. The internal parts survived the drop without any damage - yay!
Definitely not an easy repair. The repair took me more than an hour.
You'll need a good brain or some sort of system to know, where which screw goes...
Phillips #00 Screwdriver
Tri-point Y1 Screwdriver
TR6 Torx Security Screwdriver
MacBook Pro 15" Unibody (Early 2011-Mid 2012) Upper Case