If you don't need to keep your jobs or catalogs on BE1, then there is an easier way.
1. Disconnect the MMS servers from the CAS so they end up in standalone mode.
2. Make sure that all the MMS servers are in standalone by cycling the services on them and confirm in UI that they are no longer "managed backup exec" servers.
3. Decommision the BE1 server. (I recommend keeping it for a while, as long as you need the catalogs on it for a possible restore.)
4. Make one of the remaining standalone servers the CAS
5. Join the remaining standalone server too the CAS.
6. Skip this step if you didn't have centralized catalogs or if you don't want the catalogs from the old CAS. If you had centralized cataloging enabled before, you could shut down the BE services on the new CAS, and copy the old catalog files from the old CAS(.FH and .XML) into the root of the new CAS catalogs folder.(C:\program files\veritas\backup exec\catalogs) and then start the BE services. During service startup BE will pull the original catalog files from the root of the catalogs folder and place them in the correct subfolders.
Give support a call if you need help or have any questions.