Hi John
Welcome to the Forum
Before you do anything check the fuses in the boot make sure the fuses and relay are all good and seated properly
There is a pneumatic distribution and control unit which is attached to the pump if the car has 4 wheel air suspension it can raise or lower to keep things on an even keel. Check www.realoem.com put the last 7 digits of your Vin into the search box it will bring up your model, then search the relevant section. There will be a small exploded drawing showing where stuff is and Part numbers to make sure if you are buying you get the right part.
Then Google is your friend to find the part you need at the best price
Dave