I'm no expert on firewalls, so perhaps this might be usefull to you too...
I had the need for a router/firewall system aswell, and tries all sorts of stuff like customizing RH6.2 but that was way to difficult to understand for me yet... Tried looking for other solutions, the LRP fro instance, but still it wasn't really for newbies.. and then I saw the light
Freesco, a single floppy router/firewall especially for newbies, does the work, easy to configure and maintain, runs of floppy or HD, really nice...
http://www.freesco.org