You may also have a look at documentation for RHEL 4. The cluster stack has been modified for RHEL 5 and you should use conga with luci+ricci but you will get a better access to the cluster capabilities if you modify /etc/cluster.conf directly.
The cluster wiki  is also a nice place to learn about the Red Hat Cluster Suite.
Also one important tipp: don't bother with GFS2. It is not ready for production, yet.