air shock replacement

I was doing a search and couldn't find what I'm looking for. Can someone either: 1. Point me to the right post 2. Explain the Air Suspension to me. What components do I need to check to know if it has in fact gone out? -I hear the compressor when the car is on, for like a minute or so. -I was...

Car is 99 Park Ave. Had frozen LR shock. Car has auto level control. Removed air tube from old shock and plugged into new with minimal problems. Went on to do RR. Air tube will not come out of nipple on shock. Removed clip, pulled, wiggled, twisted. Even tried pressurizing system with auto level...