Yeah, there should be overhead incandescent lighting in this car and if you look up at the roof through the windows you should probably see a strip of "Streamlighting" in place with multiple bulbs inserted along it. From memory the bulbs are wired in series and if one is out the others will not light. There may be a separate wire to the rear marker lights. None of my K-Line cars of this vintage have any other form of lighting so I am guessing yours is the same.
Also from memory, K-Line cars of this era usually came with a package insert that explained how to replace the bulbs. Boat-tail observation cars are a little finicky but at the front/blunt end there should be two screws through the frame that hold the end/vestibule cap in place. Removing those should enable you to remove the end cap and expose the connection between the wires from the trucks and the lighting strip. Detaching that should allow for the strip to slide out - they are usually mounted on a part of the roof that is T-shaped.
