I've replaced the original hard drives with mSATA, 60GB cards on three iBook G4's, and have found that for this Amateur, they are not at all difficult to work on. I use the black spudgers ( fiber reinforced ), and the cases have all snapped apart with no damage...just take your time, and see what needs to be done to gently get the case to come apart.
The one area that DOES present a chance for disaster is near the end of the disassembly, when all that's left before gaining access to the HDD is the aluminum sheet: I saw one video where the commentator mentioned how 'easy' it was to ruin the motherboard when a few, small white plastic connectors were pulled apart so as to allow the aluminum sheet to be removed...
...so: DON'T PULL THE CONNECTORS! Leave them alone, and just cut the sheet so as to allow it to be lifted away. I forget at this moment where I made the cuts, but I simply used a sharp blade to make a few slits between the wires and the nearest edge of the sheet, and as the sheet was lifted away, the wires were undisturbed. Reassembly was also very easy, and a piece of tape can be applied over the cut areas if you're so inclined.
Michael.