Answer
There isn't a single documented step-by-step procedure for this specific scenario, but a confirmed working approach is: update the LOCATION_ADDRESS value directly in the relevant Document Management repository-address database tables to point at the new server address, then spot-check using the Document Object Connections screen to confirm existing documents are still attached and viewable. Take a full backup (or at least export the current values) before making this kind of direct table edit, since it's not a supported client-driven configuration change — verify carefully against a test/non-production copy first if at all possible before applying it to Production.