There are so many special tools needed, about 5, besides an OBDII scanner, I would reccomend getting the trouble codes either from a dealership or reputable repair facility.
There are tests for; short to battery, short to ground, rife height sensors for each bag, pump relay, Vehicle Diagnostics Module communications failure, Timeout failure, ECU communications error, Vent solenoids, spring solenoids and at least another 12 that would be a real dominating task to try to do on your own.
It is far more complicated a system than I suspected. With so many electronic and electro-mechanical parts, someone with all the proper testers and connecters will really be the best way to go.
If you need any help or have any questions about the codes that come back, please come back and I will be glad to walk you through this until it gets figured out.
If you have any repair/labor warrantee on work, I would go to shop that did the rear suspension work, be nice and push a little for some, "Good Customer" or good will help.