The automatic document feeder unit assembly on my HP OfficeJet Pro L7680 AIO printer needs to be replaced. I have located the replacement part (C8189-60005) but I need instructions on how to install it. HP Technical Support says they don't have those instructions, and refers me to my local Authorized HP Repair Center. The Repair Center says they only service laserjets because inkjet printers are "consumer serviceable." I would appreciate a link to documentation on how to replace this part.