If you only need to remove the scanner window and don't want to go through the hassle of dissembling the ADF:

1. Remove the seven T8 screws around the scanner window and the two behind the control panel.

2. Lift up on the front of the window assembly to loosen it

3. Close the scanner cover/ADF.

4. Lift the scanner window assembly from the front up and back, being careful of the cable running to the ADF at the back right

If you try to open the window assembly with the cover/ADF open, it will bind at the back as the hinge is a single piece that's difficult to take apart.