Disconnect the blue connector near the top right screw of the heatsink (display cable, circled in red) by pulling on the blue tab gently. Gently push and/or tape the cable to the chassis away from the heatsink.

Slowly unscrew the 4 screws holding the heatsink in, unscrewing each one at the same time, and not one at a time. The recommended screw turning is 1-2 turns per screw. The heatsink will slowly lose pressure and come off, and the screws will make a light click when they are loose.

Carefully lift the heatsink from the side with the screws, making sure to pull to the left to free the exhaust side.