Replacing Domain Controllers

I am in the process of replacing domain controllers at a central site and 3 remote offices. The 1st DC and two others are in the Central site and each remote office has a DC of it’s own that handle DNS,DHCP. The Global catalog exists on the servers in each remote site and on 2 of the three DC’s at the Central site.
My plan is to install two new DC’s at the Central site then move the FSMO roles to the new DC’s. Once dns is replicated I will then run DCPromo to remove the older servers.
Do I need to worry about replacing the DC that was the 1st install to AD? I have a single domain forest.