Uninstalling Exchange 2003 in a Office 365 dirsynced environment

I have a scenario where i need the right path.

We are having an Exchange 2003, we just did a migration to Office 365 (Exchange online), using MigrationWiz. Users are Dirsynced to O365. We are using ADFS. Everything works fine. The Old Exchange 2003 is not used any more.

Next step is how I uninstall the Exchange 2003 server, without tampering with the running Office 365 Solution. The server must die, it is on old hardware, and we have no need for it any longer.