There are multiple ribon cables and wires connected to the top case. Make sure to complete all of the following:

Remove the ribbon cable connected underneath the rear right display hinge cover. Use a plastic spudget or plastic tweezers to lift the connector up. You wil then need to slide the ribbon cable towards you and out from under the housing.

Disconnect the trackball ribbon cable from underneath the trackball assembly.

lift the top rear case back to expose two connectors for the power switch and volume control.

You can now lift off the top rear case and set asside.