Remove 6 Philips #2 screws that secure the upper chassis to the lower chassis.

The upper and lower chassis should simply lift apart.

Disconnect the two printhead ribbon cables (careful to keep them in that layered order when reassembling!) and the sensor connectors, which simply lift out.

If your print bed is not in the fully-forward position, and the lid is locked: there are two spring-loaded manual release levers on the bottom edge of the printer. Simultaneously slide them towards the front of the printer while lifting the lid (requires 2-1/2 hands) to override the lock and free the lid to open the chassis.