I have a G3 PowerBook and it worked fine with "install-gui gui-old atyfb128". You have a different video card though, so the last part would be different for you.
I'm downloading the Cooker for PPC now, and if I can figure out how to make the CD's, I'm going to give it a try. I really like Mandrake better than Yellow Dog, but the only problem I have found is that I can't get my sound working in 9.1. Hopefully that will be fixed in 10. If not, I guess I'll have to wait till May and get the next version of Yellow Dog which is going to be based on Fedora. I've tried installing Fedora's PPC version, but can't get the video working right there.