Passengers are shown boarding the aircraft from the right side of the airplane (entering and turning left toward the cabin.) There are no passenger doors on the right side of a DC-9.
The boxes containing the oxygen generators are marked "AOG" which means that they contain parts required to return a grounded aircraft to service. The generators were not AOG parts as some could be missing from an aircraft and not ground it.
The "DC-9" cockpit is a generic set. The main windows are incorrect and there are no "eyebrow" windows visible.