1997 Lincoln Town Car air suspension bag light

Hi around the 4th, my brother in law changed my back brakes, my car worked fine, but weeks after my check air suspension light came on , I was able to drive the car, however now it is like trying to ride a bull. The whole back end is down and I do not know how to fix it. I did notice like a air sound under the hood like a hollow air sound, I have been told if I change the compressor I may still have a leak, I was told to get an air suspension kit and bypass. I want to have this thing work long enough to be able to drive to a lot and to trade it in. Please help I am unable to drive my car at all.