Well, it turns out that YOU CAN'T INSTALL IT AT ALL.
Dammit.
First, the FCP 3.0.2 installer for OS X runs in Classic mode. I don't have a classic folder. So, I put my PB in Firewire mode, ran that, and the installer runs, but then says that 10.0 is not on this computer.
So I'm f----d.
There's probably some way to boot 10.2 off my Firewire drive, install it, and then move back to Panther on the G5's internal drive, but for now I'm completely screwed.
Mike