Renaming server 2003 domain

[q2418130103p]

I have a network with a DC that is also a sharepoint server and CA, and a member server that runs exchange.

I just got a second server.

I want to make this new server be the DC withe the global catalog, and also run sharepoint, and I want the old server to be the backup logon server.

In the process I also want to rename the domain.

Should I install the new server and transfer all roles to it then run the microsoft domain rename tool, or should I install the new server as a seperate domain in the forest (with the domin name i want to use) then migrate all the other systems over to it?