This video will explain how to replace the airbag / airspring from the rear of a BMW X5 E53 chassis. This vehicle is equipped with 2-axle air suspension. The procedure defined here may be different for the single axle setup.
Trim removal tool can be found here: http://amzn.to/GYcJgu
Flare Nut Wrench tool set can be found here: http://amzn.to/13rhDbC
Note: THE USE OF THIS DIY IS FOR YOUR REFERENCE ONLY. I DISCLAIM ALL LIABILITY FOR DIRECT, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES OR INJURIES THAT RESULT FROM ANY USE OF THE EXAMPLES, INSTRUCTIONS OR OTHER INFORMATION IN THIS DIY.