We have successfully deployed SCCM2012 with a different site code. Clients are all migrated and our 2007 server has been shut off and everyting is running without issue. So we are ready to retire our SCCM2007 server. Given we have 2012 deployed, is there anything special required? I know some programs that are not aware they have been succeeded, so when you uninstall them they undo AD settings and other things that break the newer version of the program.

Our SCCM 2007 environment was a single server for everything except the DB installed on a separate SQL server.

Thanks!

Not much really needed. The only thing that ConfigMgr truly leaves behind are the objects in the System Management container in AD. If you perform a clean uninstall of ConfigMgr, it should remove these but you can simply delete those manually also. For the DB, you can simply delete it and the SQL instance hosting it if it's not used for anything else. If you had DNS publishing enabled, there may be a record in DNS also that you can manually delete but this really is minor.