It's pretty simple, you just have to be careful and patient. Note, however, that I have the same powerbook and the 5400 hitachi I put in it was louder and made the fan run sooner. I eventually put in the old drive and realized that the performance wasn't really all that great. The biggest difference I noticed was that contextual menus popped up more quickly, but since I've gone back to the original drive I haven't really noticed it slow down.
BTW, maybe you can answer a question for me: how soon do your fans come on? Does the fan on the right for the power supply come on relatively quickly? How about the one on the back?