I had an old MacBook that sat unused for years. My son wanted to flex his programming skills in developing apps, and I thought it would make the perfect platform. It used to seize quite a bit in the day, and remember leaning it was the drive. It also came with 512 megs of RAM. Not much.
I've never had such a hassle free experience. We literally yanked out the old RAM and drive, popped the new ones in, installed the new O/S, and it all went without a hitch.
None. ifixit covered everything soup to nuts. If you have an old Mac, these upgrades are a snap.