Upgrading W2K Domain to W2K3 Domain

I have an existing Windows 2000 domain that has 2 DCs with the FSMO roles split between them. I need to replace these two servers with one Windows 2003 server. How should I go about this?

The second DC is also hosting Exchange 2000 (I will be using EXMERGE to retrieve the mailboxes and import to a new, seperate W2k3 server)

What steps should I follow to have a successful migration?