Don't go to an overclocking forum as they attract the wrong type of internet users who will scold you for using PowerPC while they circlejerk to their riced Windows desktops.
In regards to rebuilding the LCS there are a number of guides. However, unless the system is leaking there is literally no reason to mess with it at all - G5s run very hot anyways ( up to 50 degrees celsius, and you'll see why I got rid of mine - I want a computer to run 24/7 but not burn me up in the process!! ) and rebuilding the syetem will only make minor difference.
Here is the one that Floodgap.net ( whose webmaster uses a G5 named Bruce as his daily driver ) wrote up on the subject:
http://tenfourfox.blogspot.com/2014/04/long-life-computing-plus-quad-g5-cpu.htmlIn addition you may find this website very useful:
http://g5center.net
