Long story short: my second-hand 2.0GHz CD 15" MBP needed TLC, from its slowly dying optical drive, to is overheating logic board. I also wanted to see how easy [or hard] it was to completely disassemble and reassemble my machine, esp. since I have had experience doing so with Windows laptops.
The entire process, thanks in large part to iFixit guides, was seamless. I was rather stunned at how easy it was to get to the logic board, reapply thermal paste, and put everything back together again, not to mention outfit the SuperDrive bay with a new HDD.
Just make sure you have a lot of time and patience when doing such repairs and upgrades; ANYTHING can happen.