Yes Indeed a step was forgotten. You need to flip open the flash module. Now you can remove a small screw from the front that holds the stereo L R microphone in place, after that carefully remove the microphone cover. After that you will see a screw from the top view where the cover of the microphone was removed. When this screw is removed the back cover comes off. Please be careful because there are two ribbon cables, one for the buttons and one for the LCD screen.
PS I still have problems after replacing the complete lens assembly with sensor. I think Nikon updated the firmware and something in the firmware is faulty. Because I can still record movies but cannot make pictures (shutter button works)… Yes I tried hard reset, factory reset. No luck at all. The backup battery in my device is flat also…. Maybe I should buy another camera. No more Nikon for sure. Camera wasn't even used that much, meh ..