The process for migration is outlined in the "LicenseManagementGettingStarted.pdf" doc that's on the Estimating installation disc.  You can get the new server location setup and running before pulling the literal plug on the old LM server.  

In some rare cases, individual machines have had an environment variable put in place called "LSFORCEHOST" which points to the machine name of the LM server, obviously this would need to be changed and pointed to the new machines name.  This too is outlined in that pdf.

Hope that helps,

Chris