taking a backup of the existing vWLC configuration & modify the management & any other dynamic interfaces IP (on the same corresponding vlans) if you require to keep both vWLC up any given time.
Then once you build the vWLC with basic configs, you can download the modified configuration.
Refer this to see the CLI commands if you prefer doing this in that way
http://mrncciew.com/2013/01/25/backup-restore-wlc-configs/
HTH
Rasika
**** Pls rate all useful responses ***