Gee By default, updates for GrapheneOS apps and components (including Play Store/Services/GSF) are automatic. You can configure this in the settings of the Apps app. I think it also sends notifications about update availability and update success, by default.
But Play Store and Play Services are mostly kept up to date by Play Store itself anyway. This is also an automatic process, although Play Store does need permission the first time it tries to update itself or Play Services. GrapheneOS should display a notification to display that initial dialog for allowing the update. After that, Play Store updates are automatic and don't send notifications.
You can see when an app was last updated and which app installed it by going to the bottom of the system Settings page for that app.