Hi Jim-
When you open the support case, we'll respond with a form detailing the deployment options available for customers, which include self-signed certificate, replacing keystore, etc. We'll confirm timing for a WebEx, so our Engineers can log into the Engine and implement the changes.
When the certificates are installed, it will require a brief outage for the management service running on the Engine, but this only affects the UI and any jobs running or scheduled to run; existing VDBs will remain online during this activity. The actual outage for this activity should be a matter of minutes, not hours.