Connecting two Windows 2003 PDC’s

I have two offices connected by a PTP T1. One site has a 2003 SBS set as a PDC. The other site has a 2003 STD Server set as a PDC. I need to demote the SBS and make it a member server on the STD Network. I know that on a 2000 server you have to use dcpromo. I’ve been told that you do not have to do this with 2003. How do you join the two networks?