I need help with my air suspension.

I have a 2003 rover Discovery. The leveling system doesn't seem to be functioning properly. the rear passengers side leans to the right and sometimes the rear will just drop all the way down. I have the down hill assist warning light on, the TC light and the ABS lights.

Any suggestions as to where to start with this problem? Also, how to I figure out if I have a remote leveling system installed? This car was purchsed used by my GF a few years back.....

Thanks,
Steve