Server 2008 AD replication over 2 networks

When you say they are on the same domain do you mean that a second DC was added to the domain hosted by the first DC?
In which case they must already be comminicatinf with each other and replication will be happening without any intervention.

If however you mean that two seperate domains have been set up and they two domains happen to have the same name then this is a different matter - even though they have the same name they are seperste domains, thay are not going to talk to each other and you are going to have problems creating a trust between them if they have the same names.

The two servers were setup and installed in one location and then physically moved to seperate locations

http://technet.microsoft.com/en-us/library/cc755994(WS.10).aspx
 http://technet.microsoft.com/en-us/library/cc772065(WS.10).aspx
 http://technet.microsoft.com/en-us/library/cc739941(WS.10).aspx#w2k3tr_repup_tools_tjlt (network ports used for replication)
You would need to create a site to site vpn between the two sites ; add the two domain controllers in active directory sites and services , make sure your firewall is allowing the ports required for replication and you will be good to go.
 The links will also give you a good insight on how to optimize replication.