proper way to decommission an Azure AD Connect server

Hi - 

I inherited a really old Azure AD Connect server (v1.1.343.0).  Per Microsoft's suggestion, because it was so old, I created a new server and did a swing migration onto it (v1.2.65.0).  I'd like to retire the original v1.1.343.0 server, but can't seem to find doc on the proper way to do it.  Because I inherited this implementation, I don't want to retire this old server incorrectly and mess up our synchronization.

Can someone share the proper way to retire this old server?  

Thanks,

Gina

skigirl1