At the top of your printer is a transparent plastic window. It's only held in by flat tabs, no screws or push clips. There are four tabs at the front edge, and four tabs at the back edge. There are no tabs on the sides. So open the front door, hold the window with a hand on each side of the pane, and pop it out.

If it's really stuck, you can try prying it out with a plastic spudger or flat head screwdriver, but be very careful of scratching the window pane or the case. Protecting them with masking tape is a good idea.

This is optional for a full teardown, since you don't need to remove the window to get the top panel off, but it's handy for accessing your extruder in less dire situations.