I successfully replaced the hard drive in a dual usb iBook.
I scooped up this iBook before it was to be recycled. The keyboard is damaged, but most of the keys still work. I still need a dedicated power adapter for this unit. The 20Gb hard drive that was in it didn't work at all. I could get the iBook itself to boot off another iBook using FireWire target disk mode. A friend had given me a couple of old hard drives: a 5Gb and a 20Gb. I dismantled the iBook, removed the old non-working HD and in went another old HD: the 20Gb. I powered it up by borrowing a power adapter from another Mac, booted Mac OS X Installer from CD, and ran Disk Utility and it found the drive and I was able to format it without any errors: success enough for me.
The next part of this endeavor is to put the pieces back together again.
It was good practice to do this on this less than cosmetically pleasing iBook. I could make mistakes, read "break things", and not feel too worried. My goal is to eventually put a 16Gb Solid State Drive in my "good" iBook without destroying it in the process. Next time, I would use some kind of plastic lifter or wooden stick to pop the tabs. A metal screw driver tends to chafe the case.