New Domain controller, Need Help

We are a small business that is getting a new server that is to be used as the New ?Primary Domain Controller? This will replace an existing domain that approx 10 XP boxes login to. The server is currently handling DHCP, WINS, Login, and file storage. What is the easiest way to replace the old server with the new without having to worry about the profiles on the user machines? Or basically not having the users even be aware of the switch. Will I be able to change the domain name, or will it be easier to leave it the same?