Hi Joe,
As you will be building a new server with the same configuration as the old one, once you shut down the old unity and put the new one in production you should be good to go. I checked the SCCP compatibility matrix and Unity 7.0 is compatible with CUCM 4.1.3.
http://www.cisco.com/en/US/partner/docs/voice_ip_comm/unity/compatibility/matrix/cutspmtx.html
However, you might want to double check the integration and see that the ports register properly and that you are able to dial MWI numbers, and so on, but in theory there should be no issues as CUCM will see the new Unity as another endpoint and you will only swap it.
Regards,
Tere Stevens
-----
Cisco Systems
Unified Communications PDI Team
www.cisco.com/go/pdihelpdesk
Regards,
Tere.
If you find this post helpful, please rate! :)