I just received a G4...semi-swap, semi-gift...all the way fun!

I'm not sure which model it is and would like to soup it up a bit.

I think it's of the 400MHz vintage...blue plastic front, the motherboard has a copyright date of 1999. 4 RAM slots (none are populated), ATI Rage 128 video card (and I am sure out of practice as I can't tell if it's an AGP or PCI slot...it's not as long as the other slots). The three bigger (PCI) slots are labeled 33MHz and the smaller one (with the video card) is labeled 66MHz. On the back is written "Family Number M5183".

I'm wondering which RAM chips I should use and how much RAM can be put into the thing. How amenable and meaningful would a CPU upgrade be? I'd like to use the thing as a test box for OS X server.

Thanks in advance!