As far as hardening is concerned check out
http://www.bastille-linux.org/ I have not used this tool but it has
gotten good reviews in the press as a tool to harden rh and mandrake.
If you want a dial-up server using PPP -- Like an ISP -- check out this howto
http://www.redhat.com/support/resources/tips/Dialup-Tips/ppp_server_tips-1.html
Its quick and dirty but I have used it...