BMW Repair: air bags (suspension), lr tire, time kevin

Question
my wife was driving our 2000 540 it and the rear end sagged all the way to the ground.  I can hear the compressor kicking on and I pulled off the lr tire and you can hear and feel the air coming out of the air bag. I was wondering what the cost to have it replaced was and if it was something i could do by my self? Also I was wondering if this is a common problem or is it just time the car has 75,000 miles on it thanks allot.

Answer
Nathan, the airbags are expensive, I can't get the price right now. They are pretty easy to change. The rubber air springs will become worn and rub through or rupture. If they are dry rotting then I would recommend replacing the other one aswell. It is a common problem over time.
-Kevin