We have a domain controller at each branch office running a subnet of IPs for that branch.
Currently one of the branch DCs is running 2003 server and we're wanting to replace it with 2012. This DC is NOT running any roles on it.
The new server has DNS and DHCP configured. The plan is:
1. Bring it online at the branch.
2. Lower DHCP renewal on the existing domain controller
3. Turn off DHCP service on 2003 and turn on 2012.
4. If nothing comes up (as there are no roles to move) demote the 2003 after a week.