4.8is Air Suspension Control Unit Installation?

Im looking for an installation of this part:

http://www.ecstuning.com/BMW-E53-X5-...onics/ES66456/

i recently got a message on the dash saying self-level inactive took in to bmw they replaced the struts hour after getting it fixed same thing. i read a few forms and found out that its usually air bags (pneumatic shocks), the air pump, rear sensors, or a few of both.

I am looking for a installation guide on replacing the air suspension control or just any information that could help me out._a_