I can think of two ways. First, introduce the new machine, and move the mailboxes. Then remove the old machine. Some DNS work and I would have to visit every client machine to remap to the new Exchange Server. Second, replace the machine and perform a backup of the databases, and restore on the new machine. What would you suggest?
Note that you will not need to visit the desktops. In the case of the Same Server Name method, to the clients nothing has changed. In the Swing method, the trick is to leave the old Exchange server running for a couple of weeks before decomissioning. When the Outlook client is started the Mail Profile on the workstation tells Outlook to connect to the old server. The old server refers the client to Active Directory, which says your mailbox is over here at the new server. And Outlook then updated the Mail Profile.
However, if you are going to go through this anyway, perhaps consider using the Swing method and Move the Mailboxes to an Exchange 2003 server.