We are going to be replacing some of our Windows Server 2003 remote site servers with new servers running 2012 R2. All of the remote site servers are backup DC's. They are all on our WAN. They hold no FSMO roles. At our main site, we have our primary DC's which are 2008. I am looking for some good advice on performing this task cleanly and efficiently. We are ordering 6 replacement servers shortly. So, I will have them all at once.