Decommissioning a domain controler

So i have been following this Kb here http://technet.microsoft.com/en-us/library/cc755937%28v=ws.10%29.aspx

on decommissioning one of my old DC witch is 2003 and I am going to replace it with a new 2008 r2 DC The question I have is do i need to remove it from the replication in sites and services before i demote it? Also this is DC is also our old Exchange 2003 server. who ever set this domain up decided it was a great idea to put a exchange server on a DC. Also a side note I been have been having an issue getting exchange to uninstall as well with a c1037ae6 error. We have since moved to exchange online in office 365. Is it ok to delete the Exchange service out of the adsi under configuration since we wont have a on premise exchange server anymore?