(I'll fill in more info in this post as I find the time)
Tools and Supplies (roughly)
Beloved 12" Powerbook G4... my first mac
Touchscreen tablet from Ebay: $50
Arctic silver CPU thermal paste
1 mini USB 2.0 A male to A female cable
Fine toothed hacksaw blade for metal cutting
Hammer + 1 nail
Tiny screwdriver set
Gray electrical tape
Anti-static tape (preferably, but not necessary...)
Wet sanding block (hard foam), something like 220 grit will do
This was actually easier than it seems. The blade cut through the aluminum like butter. Also, instead of sawing through the last edge, I scored it several times with a utility knife and bent it back and forth. It snaps off eventually, leaving a straight edge. :) I then applied a long piece of blue tape along the jagged edges and used it as a guide to straightened the cut out with a metal file. Lastly, the fine sand paper was used to smooth out the edges some more.
I found out that Nvidia cards in the powerbook models cannot do display rotation... This was annoying because the vent was facing toward me, blowing hot air out as I used the tablet. I ended up opening everything again to flip the actual display upside-down. The cable to the LCD's inverter board is really short, so it had to be made longer by soldering together an extension.
The USB cable that came with the touchscreen was replaced with one that is thinner and flatter so that it would lie behind the screen better. Unfortunately, it isn't shielded so the touchscreen didn't work at first. After proper shielding with some more handy aluminum foil, all is well. :)