If you haven't done so already, remove the speaker assembly on the right by loosening a single T-10 (2.5mm x 14mm) screw.

Remove the two T-9 (2mm x 7mm) screws from the bottom right and left corners of the RAM slots that secure the black plastic bracket to the frame.

Now simply lift out the logic board while keeping a careful eye on all those wires you just disconnected. The heatsink fins are attached to the logic board and lift out with it.

Note: There is a bit of foil tape on the far right (by the audio ports) that will need to be pulled up from the case as well while you lift out the motherboard.