The airbag is mounted onto the steel part of the door and doesn’t come of or doesn't need to be disconnected when you take off the door panel.
There is a screw behind the plastic SRS-badge and there is one behind a plastic cover in the arm rest, one near the door handle and...as far as I can remember that is about it (it has been a while since I last removed one).
The door panel itself is attached to the steel plated door by plastic clamps that need to be pulled away straight from the door (be gentle since the clamps are just plastic --> mercedes way of saving money) and the top of the door panel along the window has to be pushed upwards along the window after the plastic clamps along the bottom and sides are all loosened.
good luck & greetingz,
with a minor 600+k