When using the generator properly connected to the included transfer switch the circuits in the switch are properly disconnected from the utility service. So, when your utility service returns the other circuits in your electrical panel are going to be powered while the generator circuits are safely disconnected from them. When your other lights and appliances come back on you will know.
The maintenance is listed in the owner's manual available on the site and comes with the unit. Typically it will be oil changes, oil filter changes, air filter changes and spark plug changes. You will have a maintenance schedule to follow based on the usage time of the unit.
All service is performed by your local manufacturers service dealer who handles all warranty and general service on the generators. You can find on via the following link....
How To Find A Local Service Center