Now that you have the main board out of the way, you should be able to see the back of the sensor board.
This sensor board is attached by three screws, all the same length.
The top screw is hidden by a bit if black tape, you can remove this and keep it safe. Don’t stick it to anything made of paper as it will render it useless, try something plastic. If like me you damage it, try using a small bit of electricians tape.
Also take a note of the gold prongs, you will need to put these back in the right place afterwards.
Once the screws are removed the whole sensor board will come away, and you can see right through the camera.