Anyone have any howto's or manuals on how to setup Reverse DNS on a WHM/CPANEL box?

do a search on the forum - there are a couple of posts covering this. Also a google search on "reverse dns" turns up some good stuff like http://www.tldp.org/HOWTO/DNS-HOWTO.html .

I also (and I know I've said it before) HIGHLY reccomend the O'Reilley book DNS & Bind by Paul Albitz and Cricket Liu. If you look on ebay you can sometimes find it quite cheap.