samba - May 2013 - Upgrade Samba 4 alpha 18 to Samba 4 stable version

Hi,

We are still running Samba 4 alpha 18 for our servers, its integrated with
postfix/dovecot, sugarcrm and a samba 3 fileserver.

All of these systems are virtual running on Proxmox. Now we are trying to
upgrade Samba 4 alpha 18 to a stable version. We are also running Ubuntu
server.

What would be the best way to upgrade it?