Thanks jsnetman - I was thinking of imaging the current RM server (to provide a way back during the lab phase) and then do the following:
build the new server, join domain, promote to DC, transfer roles away from RM server (FSMO + file, print, dhcp etc) and then start uninstalling the RM bits one by one. Is that how you did it (or would recommend doing it) ?
It's the "hacking away" that I'm not keen on - if there was a documented / supported migration path I'd be happy to follow it, but what I don't want to end up with is a network with problems that crop up because of RM bits that are left over in AD that become a nightmare to troubleshoot.
In the absence of a documented migration path I'd probably be tempted to do a clean install - one that I know will work problem-free, rather than try and save the effort up-front only to spend twice as much time & effort troubleshooting issues later.
Are there tools you've come across that help with this or would this migration involve trawling around manually with ADSIedit to ensure all RM bits are cleaned up?
Thanks for your help!