Do yourself a favor and buy some ArctiClean... I used Isopropyl Alcohol and Q-Tips and ended up spending 45 mins scrubbing the surfaces. I imagine with the Arcticlean it would've taken mere minutes.
Do Step 35 first (remove the fan connector from the motherboard), otherwise as you pull the fans forward out of the metal bracket you risk stressing the connector's attachment to the motherboard (because the fans will press against the connector as you pull them forward).
Be careful not to lose or break the two teeny metal clips securing the optical drive assembly snugly to the metal casing on either side of the drive's front face. I used a spudger to press in the topmost tines on these clips because they were catching on the drive and bending up. The clips should stay on the metal housing, not come off with the drive.