Services in Exchange Server 2003

OK somehow I managed to decommission my exchange 2000 server after migrating to exchange server 2003. As I stumbled through the uniinstall, I noticed when I was in the exchange system manager under the "recipient update" there are two services that are pointing to my domain controller lets call it server1.

First what do these services do?

I am going to be phasing out that domain controller. My question is when I bring up my new domain controller and get ready to power down my old dc (server1) is it just a matter of point those services in exchange to my new dc?

Also is there anywhere else I need to be check for references of my old dc within exchange manager?

I'm sure these questions are easy to answer but I am increasing the points do to multiple questions