How do you remove the Cartridge door? Is there a Servic/Repair manual?

I have a part that came off one of the feed roller shafts inside the printer. I need to remove the top of the printer (HP calls it the Cartridge Door). I need to remove the door so I can remove some of the screws holding the top of the printer casing. Can anyone help me with that? Also, is there a repair/service manual available that would assist with disassembly of this particular printer. Thank you