How do the air bags on a 1993 Lincoln Mark VIII decompress to make the car sit lower and can it be done by anyone?

45 seconds after you turn the ignition off, passengers get out (no weight on the front seats) AND you close the doors, the system will automatically vent and drop the car by one (1) inch. If any of those three conditions are not met, it won't drop. You can usually hear the solenoid valves open and close when it is doing that. When the engine is started, passengers get on or off and doors are open and closed, the system will check and adjust for normal "city driving" height as needed. When driving at speeds over 60 MPH for more than 45 seconds, the system will vent and drop the car by one (1) inch for better stability, raising it back to the normal "city driving" height when the speed drops below 40 MPH for more than 45 seconds. If the car is unevenly loaded (portly passenger on one corner, for example), the system will automatically adjust and level the car. Venting is done by opening the individual solenoid valves on each bag and the master vent valve on the compressor with the compressor off. Inflating is done by turning the compressor on and opening the individual solenoid valves, with the master vent valve closed. Front bags are controlled individually, rear bags are controled in tandem.