To get the mac on the network I would use the ethernet connection...all macs have ethernet. It is then as simple as setting up a PC using ethernet.
As for the OS, could try getting it from here:
link
Probably best of waiting until you get your hands on it though before buying the OS - just to make sure that it will work with OSX, I have an old G4 (2001) that works fine with OSX - it just needs lot of RAM...