Remove the two bolts from underneath the front of the car's rear seat bottom cushion, using a 3/8-inch socket and ratchet. Slide the seat cushion forward and pull it out of the car.
Remove the two 3/8-inch bolts from underneath the bottom of the rear seat back cushion, using a 3/8-inch socket and ratchet. Slide the seat cushion up pull it forward to remove.
Pry the edges of the brake cover light up with a panel tool to remove it.
Pry around the edges of the rear deck panel with a panel tool. When the panel is loose, lift up and slide it forward to remove it.
Remove the Phillips screws holding the speaker. Lift the speaker up and unplug the wiring connector on the back.
Plug the new speaker in and mount it in the opening of the rear deck with Phillips screws.