#1 - Avoid G5s...and any PowerPC computer. THey are so underpowered they would hamper things more than help.
#2 - The only application that will work with render farms and distribution is Compressor (Well, and Shake, but that's long gone). Each computer would need to have QMASTER installed. And you enable it to then add the machine to aid in distributed rendering. Again...this would only work for Compressor. FCP, Color, DVD Studio pro...they won't work this way.
Here's the guide on what to do: