Lay the iMac display-side down on a flat surface.

Loosen the three Phillips screws securing the rear panel to the iMac.

These screws are captive in the iMac. The center screw will stop turning after about 3.5 turns and the outer screws will stop turning after about 5.5 turns. Do not try to remove these screws from your iMac.

Lift the rear panel slightly from the bottom edge of the iMac.

Pull the rear panel toward yourself and remove it from the iMac.

Lift the AirPort card slightly by its plastic tab and pull it straight away from its socket.

During reinstallation, insert the AirPort card such that the antenna side is nearest the center of the logic board.

Insert the flat end of a spudger between the body of the AirPort card and its antenna connector.

Push the spudger away from the AirPort card to disconnect the AirPort antenna.

When reassembling your iMac, be sure to insert the AirPort card the way it was before disassembly.

Remove the two 5.5 mm T6 Torx screws securing the AirPort bracket to the logic board.

Slightly lift the AirPort bracket off the logic board.

De-route the AirPort antenna through the slot in the AirPort bracket.

Slightly insert the tip of a spudger (or any other small wedge-shaped object) under the PRAM battery directly across from its retaining clip.

Do not bend the metal retaining clip up, as it is brittle and will break.

Use another spudger to slide the PRAM battery out from under its socket's retaining clip.