1 - 2 horas
The screen on my girlfriends macbook broke, we determined it was a backlighting problem. She had the repair quoted at a minimum of 350 dollars. I decided I could do it cheaper. I'm not really sure the situation surrounding her screen failure, however I am inclined to attribute it to coffee spillage.
The repair was decent. It took me two hours, which stood in contrast with my estimated one hour repair time. I've disassembled and reassembled several windows based laptops (as well as desktops but that isnt so relevant for this), gateways and dells primarily, and I can do that whole tear down and rebuild relatively quickly. The mac, however, is much more complicated. It helped me greatly to follow the instructions in IFixIt.com I did not refer to them for rebuilding the computer, however for disassembly they were invaluable.
Be patient and calm. There are more tiny screws than you would imagine. Follow the instructions on the disassembly. It will pay off.