I really can't address your question directly as I went straight from RH6.2
to RH7.2.  The upgrade wasn't all that painful, only about four hours to
apply (P133w/32M RAM), and a day or so to sort out the changes from ipchains
to iptables.  There are security holes in an un-updated RH7.0 installation.

I strongly recommend the IPMASQ HOWTO at www.linuxdoc.org, it's worked every
time for me.