I am having a similar problem, only the server in question is an SBS2003, so AD, Exchange is all lumped in one.
I have got as far as reinstalling the OS (didn't continue the setup to configure SBS). I've pushed out the remote agent to the new server.
Now, how do I restore the system partiton and system state to the box? I am restoring to the same hardware.
How do I get BE to restore to my server, considering that I can't do this unless it has the same name/domain membership, and I can't join the machine back to the domain because the DC computer object still exists?