@bobsuruncle:
ah yes, good idea. what's the best way to swap it without re-configuring everything?
Download and edit manually your config.xml is the best way, I think. Always use saved copy for backup!
Search for interfaces, ex em0 and em1 and swap them everywhere (match whole word only). For my setup it counts only 1 match for every interface assigned. After editing double check everything and restore your edited config on firewall using gui.
The other way is just to reassign it via console menu or even gui, but I did not try this way and it could be complicated as you need to re-plug your cables on the fly may be.