iFixit

Tape the EMI shield to the face of the display to keep it out of the way.

Remove the two 5 mm T6 Torx screws securing the display data cable connector to the logic board.

Pull the display data cable connector up off the logic board by its black pull tab.

Peel back the EMI tape from the two vertical edges of the display.

During reassembly, it is helpful to use several small strips of tape to hold the EMI shielding along the left and right edges of the display footprint out of the way before lowering the display into the rear case of your iMac.

Allow the lower EMI shield to hang down from the display.

Remove the four 7.5 mm T10 Torx screws securing the display to the rear case.

The screws are recessed, so a thin magnetic screwdriver aids in removal. Most bit drivers are too short to reach these screws.

Lift the lower edge of the display and rotate it toward the top edge of your iMac.

Do not lift it too much, as the inverter cables are still attached.

Disconnect both inverter cables from the inverter board.

These connectors are seated very tightly in their sockets. It is helpful to use your fingernails or the tip of a spudger to push the ears on either side of the connectors to dislodge them from their sockets. A small pair of hemostats helps a lot.

Disconnect the two inverter cables at the top edge of the inverter using the method explained in the previous step.

Rotate the display until it is nearly perpendicular to the rear case and lift it up to peel it off the EMI shield stuck to its top edge.