Hi Chris
You'll need to reinstall both "new" servers. The Pub from the 2nd office would need to be rebuilt as a Sub anyway. Your Sub from the other office wouldn't know about the current cluster and would also need to be reinstalled from scratch.
If you want to retire your existing Pub (and replace it with one of your new servers) then you're looking at DRS backup and restore of the current Pub onto the replacement hardware.
A fair amount of work to do I'm afraid.
Hope this helps.
Barry Hesk
Intrinsic Network Solutions