Very easy, very straightforward
30 - 40 minutes
My trackpad stopped working because of water (most likely). The trackpad could respond to scrolling, dragging, and pointing but not tapping, which meant not clicking or double clicking.
The repair guide was incredibly detailed and hit all the major aspects of the repair at hand. No qualms. I often turn to ifixit for all my repair and teardown needs.
Yes. When you are installing the trackpad, and the computer is upside down (ie you can see the logic board), consider placing a handful of paper between the screen and the keyboard. This will create enough resistance so that when you are re-attaching the small screws to hold the trackpad in place, you can put pressure on the papers not your screen.
Otherwise, good luck, and godspeed.