Spilled milk on the trackpad of my MBP and had to replace it. (MacBook Pro 15" Mid 2009 2.53Ghz)
Used the repair guide for replacing the upper case and purchased tools and an upper case to do the repairs. Went swimmingly until step 34--removing the display hinges. The screws were so tight that I twisted loose the handle of my new T6 screwdriver, then broke the tip of another T6 driver. So, frustrated, I gave up on replacing the whole upper case when I noticed how the trackpad could be replaced without removing the display, etc. So I returned the upper case to Ifixit (thanks guys), bought the trackpad and a pro driver set and dove back in. Voila! the trackpad went in pretty easily and now my MBP is up and running fine.
A few caveats though: #1) when replacing the back, one of the long screws pierced the wiring to the DC-in board and I had to replace that too. Word to the wise--be sure that DC-in wiring harness is tucked out of the way when reassembling the logic board or that screw could pinch the wires! #2) when reattaching the ribbon-style cables to the keyboard (and trackpad) one needs to be careful to make sure the connection is secure--that is, all the way in. It is easy to leave it partially out and then you won't be able to start up once it's all back together. I found out the hard way and had to reopen and recheck my connections. Upside to this is that I can open up this baby blindfolded now (LOL). Thanks Ifixit for all the support.