I just wanted a faster, larger hard drive, and needed a little more RAM.
The repair went almost perfectly, I meticulously followed the instructions in the guide, but when I went to turn on my computer, the screen wouldn't come on, and it loudly beeped at me three times (Repeating). I quickly discovered one of my new RAM chips was defective, and put back one of the old RAM chips until iFixit sent me a replacement. iFixit sent the part promptly after I let them know of the problem, and after a couple days I had a new working RAM chip, and my computer is working great.
When trying to plug back in the LED screen connection, get someone to hold the screen just above where it needs to go so you can have the use of both your hands. This step is tricky and using the Spudger for a little bit of leverage to push the connection back into place makes it much easier.