10 - 30 minutes
My power cable connector kept overheating and melting the inside of the connector. Eventually figured out that the MagSafe board needed replacing.
Smooth, no problem - followed a tip from a user to skip from step 6 to step 18, that saved a lot of work and it went fine.
When disconnecting the display data cable, you lift up the little plastic tab connecting to the shiny metal - that's a clip. Then pull the connector out. In the instructions this says "grasp the plastic tab and rotate towards..." but it's not clear.