Is it very important that the new domain controller is named exactly the same as the old one?
As I see it the process would be something like this:
1) Install the operating system (Windows 2003?) on the new soon-to-be domain controller and tune any settings you would like to tune on it.
2) DCPROMO it into your domain and move any services that might be running on the old domain controller to the new one.
3) I guess that you want to move your exchange environment as well. Then you also have to install exchange on your new domain controller (or alternatively on another member server). To not make it to complicated, you could put the new domain controller in the same administrative and routing groups that the old one was a part of (from the assumption that they both are located on the same subnett and stuff). Then you must at some point move your public folders and mailboxes to the recipient/public stores on the new server. You will need to check that different connectors and policies are with you as well ... but they should be.
You then need to change the configuration on the clients to point to the new exhcange server (this could be done throught group policies, but it depends on how your environment is set up).
Finally when everything is working, uninstall exchange on the old domain-controller, remove the services, and demote it to an ordinary member server. From there you can take it out of the system when you feel for it.
Remember, if you use DHCP, it will take some time before the pointers for the new services will be fully replicated out to your clients. Check the duration for your DHCP-lease to give you an idea of the time interval. Till then, you should run any service that you´ve moved on both servers, so they will be operational both for clients with old leases, and for clients that has renewed their leases.
