1 - 2 hours
The trackpad had become unresponsive to both touch and click.
Had iFixit not had a very clear guide to replacement, I would not have undertaken the work myself. Kudos also to the designers at Apple-a very elegant and straightforward unit.
I was repairing my work notebook, and couldn't afford the downtime associated with sending it to a repair shop, so I was properly motivated.
It went quite well, but taught me a bit about the importance of patience, particularly in the reconnection of different types of connectors.
The Spudger is invaluable.
Be careful with the Spudger in disconnecting the smaller plugs from the logic board. Popping a socket off the logic board is a costly mistake.
Getting the logic board out in Step 22 involved using the Spudger to gently lift the board in a way that pried and lifted the speaker out of its recess. Patience is required not to bend it too much or apply too much force to get the board out.
The hardest step for me was getting the keyboard ribbon cable (removed in Step 17) firmly back into the ZIF socket. Manipulating the retaining flap to get the ribbon in straight (with the help of the Spudger), and to then push it in a flat plane to get it all the way home without bending was tricky. A cheap hands-free magnifier helped.
Putting the screws in little bowls, muffin tins, or an ice cube tray can help in not losing any. Working on a soft surface that keeps loose screws from bouncing off the table also helps. If all else fails, a magnet on a stick will help retrieve lost screws (even the SS ones are magnetic.)
Consider replacing the battery at this time. I did it for performance reasons, but another would be that two of the three the plastic screw tabs on the battery that hold it to the case were broken (over-tightening at the factory, shock over time?) I've seen this on a couple of MacBookPros.
P6 Pentalobe Screwdriver 2009 15" MacBook Pro Battery
Tri-point Y1 Screwdriver
MacBook Pro 15" Unibody (Mid 2009-Mid 2012) Trackpad