Its really not that difficult, as long as you install the render engine on each of the machines, and point them all to a shared folder on one machine. Then its as simple as collecting the files to that folder. I would be leary of this in your situation though. I would suggest just letting the G5 do all the work, and spend a little extra time on it. I haven’t done any net rendering in a little while, but I do know that in the past, you would get color shifting by mixing processors in renders. For a while I ran a cross platform network render farm, but, there were differences in the frames. I even noticed color shift differences from just the P3 and P4 computers. So, long story short, give it a shot if you want, but I would suggest maxing the ram in your G5 and work on that, unless its rendering, in which case, you can still work on one of the other machines.