I don't have your answer, but thought I'd let you know your most likely the only user on Yellowdog and using a G3. If you don't get any responses it because we don't know, not because your being ignored.
Just installed Yellow Dog Linux 3.0, which is brilliant, but I cant get it to run in 1024x768 mode. I have a Mach 64 video Card running on a G3 PowerPC (i its a mac -booo, buts got linux on - horaay).
It runs in 800x600 fine, and I have tried changing the "xf86config" file so it does run in 1024 mode, but it fails to do so, it keeps reverting back to 800 mode (after complaining).