There are a half-dozen different versions of that computer. I have access to GSX. Give me your serial number and I'll look it up to get you the memory specs.

I'd use Tiger and iLife '06 if I were you. I would NOT put Leopard on an iBook G4. Not if you want to have a good experience. The experience isn't very robust even on a 1.67 PowerBook with a gig & a half.