You can download the update from your purchase history.
To update, yes, you would deactivate and delete the version currently installed. After you installed cMap 4.0, go to the Connections : Settings admin page and enter your support license key under the Licenses tab. After you do, then you will be notified of updates and have the opportunity to apply the update in-admin as long as the support license key is active. This is one of the major new features in the cMap.