Gently pull the ribbon cable by the optical assembly out of its socket.

Disconnect 7 other cables.

DO NOT disconnect the cables by pulling on the wires, but rather ease the plugs out of their sockets. They will come out quite easily if you grip them with a good quality pair of tweezers or repeatedly pull on one side then the other.

You can now lift off and put aside the main logic board by easing it upwards from the front. When you get it off you will see that it was retained by 2 connectors: an edge connector on the optical assembly and a pin block to the right connecting it to the power supply board below.

On reassembly, make sure the two connectors on the underside of the logic board are properly engaged and pushed fully home.