@CountRaven

You will need the Apple Service Diagnostics CD. I forget which version off hand it was to calibrate a G5. Surely there has to be an ISO somewhere around the internet. ;)

If you are still using the same matching CPUs, just be sure to put them in into the right slots again. For the most part, when I left the stock fans in it kept quiet, but time to time would spin up once it would get hotter. CPU Temps would be slightly on the higher side, but again the LCS calibration from before will spin the fans up as needed to move out some of the air. Don't worry, its all technically "active cooling" since all 4 fans down below spin. They spin the moment you power up the machine. :)

Do I recommend fan replacement? Ehhhh, If you are wanting to make the overall temperature of the CPUs cooler, then sure.

Good luck if you go that route. If you never have ripped apart the CPUs from the LCS then you may want to give it a look.