A guide for MRTG would be dependent on what and how you are monitoring. The defauly mrtg install guide covers everything in great detail, perhaps you can start there then ask specific problems once you acheive them.
It would be a surprise to me if anyone bothered writing a guide through forums for such a task. Do a couple searches for "MRTG install guide" or "MRTG tutorial" on google and you should find plenty of information.
That aside, the install for fedora vs RHE shouldnt differ much at all.