My Powerbook was kind of a pain, because one of the tiny screws was really stuck in there. It appears that they use 'lock-tight' or some other tightner on the screws which I think does more harm than good. But overall it's no big deal.
My girlfriend's iBook was a piece of cake, it was the last generation G3 if that matters, just pop off the keyboard, undo a screw or two and slide in the RAM.
Definitely an easy job for either computer- something that takes a little patience and care but is certainly achievable.