On the two new Server 2008 machines, install Active Directory (AD). During the install/config you can create a new AD or join an existing one. When you join it sets up the replication of AD.
If you want to replicate the users data/profiles/shares you should start reading about Distributed File System and then start to configure it
I sometimes setup a standard pc with Server 2003/2008 and setup AD just to have the data replicated, incase of emergencies (usually thats at single server sites).
Hope this helps
EDIT: How would your server get stolen? Locked room/cabinet should prevent this somewhat. Even if they got in, servers are rather heavy in my experience...