I know sys-unconfig takes my server back to the as-manufactured state, but the man pages seems to imply only for certain aspects, namely IP info, host info, disk mounts, etc.
Will this affect any software already installed? I have a piece of software installed in /opt. I don't care if the mounts disappear because I can reestablish those, but I don't want my install or configurations deleted or erased. Any ideas? Oh, the reason I'm contemplating sys-unconfig is because my ethernet adapters are all screwy. I have two but for some reason they show up under ifconfig -a as pointopoint links to the loopback address. I can't seem to find a way to undo this and I have no idea why they show up as such in the first place. Also if I have two NICs, do I need a separate host name for each adapter?

It only effects the network configuration and other similiar changes like hostname that can affect the network configuration, nothing else will be affected like software installed, etc.