I'm finally getting around to posting a description of the disassembly of Katie's PowerBook. This is what's necessary to swap out an HDD. On the PowerBook, it's a lot harder than on a typical PC laptop, since basically the entire device has to be opened. Note that this sort of disassembly isn't for the faint of heart. I've disassembled and reassembled a lot of desktops, of course including building machines from parts, although I'd only had to disassemble one laptop before. However, for the persistent, here're pointers to teardown guides in English and in Japanese.

1) PowerBook with lid closed, before surgery	2) With battery removed Most people have done this much at least!
3) With memory cover removed Note that the black screw inside needs to be removed to free the keyboard.	4) Keyboard with necessary function keys removed This is the part I would've stumbled on had I not had a reference! There are two screws under F1/F2 and F11/F12 that have to be removed.
5) With keyboard removed The cable is so short, it's a royal pain to take off and put back on. Also, after the keyboard is removed, two additional cables under foil tape have to be removed to lift off the upper case.	6) With upper case removed A T6 Torx screwdriver is needed to remove the upper case; specifically, the two screws between the display and the keyboard. Note that one has to keep track of what screws came from where, as there are a lot of them, and they have different sizes. Working the upper case free from the lower case is a pain, as well.
7) With HDD removed—disassembly complete

HDD replacement is just a matter of swapping out the old HDD with the new one and reversing the above steps. There you go, $300 saved! Might not be worth it unless you have the time and inclination, and possibly the desire to recover data on the old HDD (since Apple won't give that back to you).

And no, I didn't have any unused screws left at the end when I was done. ^_-