I don't think the procedure varies from a single server to FRHA. Been a long time since I've worked with System Platform redundancy, but there's only one true instance of the SMGR virtual machine in that setup. The primary continuously propagates virtual machine disk information to the standby and goes active if the primary is unreachable.
I would follow
these instructions and the certificate updates should be reflected in the mirrored disk data as with anything else.