suspension compressor may be shot?

I have a 2000 Discovery II. It looks like my intake muffler is broke and it has been sucking in air from underneath. It must have been sucking in water too. My rear end will not raise anymore and their is no sound from the compressor. Does anyone know how to check if it is for sure the compressor and where to get a good deal on one?

http://[I]rangerovers[/I].net/repairdetails/airsuspension/suspump.html#jumpers