Download the Crossfire service manual. There is a detailed description how to replace the subwoofers.
(I do not have a picture for each step.)
(If you have a roadster there steps to do are different than in a coupe.)

Pictured description for a coupe.

Unscrew all plastic screws and brackets at backplane.

Unscrew the mounting plates:


Remove the door seals - the hold the carpet.

Remove this screw:


Remove this cover by pulling it to the front and the upwise:


Remove the upper long top plastic cover. It's clipsed.
Remove the pouch by pressing both upper ends to the middle (clipsed) and pull it upwards.


Now you can drop down the carpet.

To dismount the subwoofer remove the 3 screw-nuts.


Disconnect the speaker.
Now you can replace the speaker.