My 2010 Macbook Pro started giving me problems about three months ago, it got really really slow (consistently froze up for about seven seconds after anything, even a simple click!) and then it wouldn't turn restart. Pulling out my handy 2008 Macbook (my beloved relic of a computer which, surprisingly still works fine) I troubleshot and determined it was a hard drive failure.
The repair went smoothly. I ordered both the 128GB hard drive (I don't use that much memory) and the tool kit, which included every single screwdriver bit that I required. The step-by-step instructions went without a hitch, and when I hit the power button it worked like a charm. ifixit is the tops!
Advice: This is a very simple repair which, if diagnosed correctly, will whisk away your worries. Buy the toolkit, because Apple obviously likes to make it difficult for plebeian society (us) to work on their products so they use all the odd screw heads; so unless you have a tri-wing screwdriver and a set of torx lying around, get the toolkit.