Piece of cake . Open the blower door and remove the 2 screws . Next remove the screw in front the on off switch. Now you can flip the top and see two wires going to the on off switch pull them out carefully. If I remember correctly one is orange/red the other blue. Next you take the top upside...
In 1987 a Kirby salesman came to the door and my mom let him in. The kid was nice but when my mom pulled out the diamond jubilee you could see his heart sink.
I would make sure the tube that goes to the piece that penetrates the bag is clear. Sometimes the small hole in the penetrating tube gets clogged and causes the door to pop open. Also it might be a good idea to cut the ends off and re-attach the 3 tubes one might not be sealing properly.
I lucked out with mine . I paid 35.00 in goodwill and it was complete with owners manual. The machine has no scratches or dents the power nozzle has very minor scuffing. I replaced the hose but swapped the handle out to match the machine.