@jamescosten after your trigger you need the "Get changes for an item or a file (properties only)". Then in your condition you select Has Column Changed: Status or whatever your column is called and you could have an extra row of Status is equal to Completed. If true then send an email, otherwise do nothing.

Rob
Los Gallardos
Principal Consultant, SharePoint, Forms and Power Platform, WSP Global (and classic 1967 Morris Traveller driver)