Gear lever cover / door cards

I need to change a torn gear stick cover on my Year 2000 318ci but I can't get the gear knob off the gear lever. It's a manual gear box and I had expected the gear knob to simply screw off of the lever......any ideas ?........

Also I have a problem with the central door locking. It hapens when I use the key to remotely open the doors, the drivers door more often than not does not unlock (buton does not pop up). But if I relock then try again with the remote the lock works as it should. I will obviously need to take the door card off of the drivers door to investigate but I am a bit unsure because of the air bag that lurks in the door.......does removing the door card affect the airbag and if so what is the proceedure for accessing the inside of the door ?. Thank's in anticipation