Mac's monitor cavity. You would find it fully shielded and very forbidding. Do yourself a big favor and don't go there . Facing the back, place your hands palms-up in front of you, and slip them under the left and right side of the underside of the panel. Pull down on the finger shaped curves on the plastic release clips and pull the panel free from the bottom and tilt it up and lift it off.
Installation is the reverse of the removal process.
Unhook the silver logic board pull-handle, pivoting it downward. Some Macs have 2 more silver screws holding the logic board rear bracket. Remove them if present. Grasp the pull-handle and pull slightly to release the board and slide it out. Installation of the logic board is the reverse of the removal process.