Ok, so just to be clear....are you trying to update the OME server _itself_ with OME? :-)
If so, this is actually not allowed...the idea is that you don't want your OME server rebooting unexpectedly when while monitoring the health of other systems. We are considering making this an optional support in the future though. If you are interested, let me know and I'll put you down for a vote.
If it is just one box, I think people use the SUU CD often for this type of thing. If multiple, then OME.
Hope that helps.
Rob