These steps should be pretty solid for you:
-Install SQL
-Install SEPM on the new machine
-During the new install, select "additional site" to replicate with the original SEPM
-Replicate all the data over, this may take time (hours)
-Create a Management server list with the NEW ip/hostname as priority 1 and the OLD ip/hostname as priority 2. Assign this to ALL groups
-Leave this setup as is until you see all/most of your clients have moved to the new SEPM
-After everyone is moved over, open SEPM, go to ADMIN, select SERVERS, and delete the replication partner listed
-Edit the management server list to remove the priority 2 holding the old machine info
-At this point you can do whatever you want with the old server
If you have any straggling clients that dont connect you can replace the sylink.xml on them to get them connected to the new sepm.
I know it was brief...speak up if you have any questions.