Removing Exchange 2010 and SBS2011 gracefully after migration to Server 2008 Std R2

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http://serverfault.com – We have recently completed a server replacement for a customer. They had SBS2011 using Exchange 2010. They now have Server 2008 Std R2 and Google Apps email. We have migrated the DHCP, DNS, Filserver and all 5 FSMO roles to the new 2008 R2 server (today). During the grace period for SBS2011 we intend to decomission the old server completely. Previous experience would suggest uninstalling Exchange 2010 then demote SBS2011 then remove from the domain and switch off. Can I simply demote SBS2011 without removing Exchange? Can't really find any walkthroughs on this. My concern is that if we sim (HowTos)