Edited
Hi,
You are changing both hostname and IP address.
You can use Replication method or Sylink replacer to restore client communication.
Note : Replication is an option, but its better not to go for that. Because if you do replication and remove the old server that is the Primary SEPM , in future if you want to do replication you will not be able to do so.
With the help of Sylink replacer tool you can redirect your clients to new SEPM.
I have sent you PM, you can try that way also.
If you have specific policies you can take a backup of policies.