Dynamic drive failure

[grr]

I recently bought a loaded one-owner low mileage 2007 X5. After just a couple of months I had a leaking rear air spring. Replaced both thinking I might just be unlucky. Well, a couple of months has passed and now I have a Dynamic Drive failure message showing up about every 3rd time I start the car.

Diagnosis reads:

DYNAMIC DRIVE (ARS) (ars_70) 4 faults
6276 Predrive check
5D5B Pressure build-up, front axle, faulty
6271 Predrive check
5D50 Supply, pressure sensor, front axle

First thought was to replace the pressure sensor (or at least diagnose it), but looking into ETK it seems the system basically consists of three parts:

- Tandem pump ($1497.15)
- Stabilizer bar ($1653.70)
- Valve block (no price @ realoem, but listed locally at around $1700)

Obviously not what I was hoping for. First of all I do not know where to start, second I was expecting it to be possible to replace sensors separately, and third... I am aware that it is a complicated system, but those PRICES...

Being my only car it is also complicated to just start disassembling it not having any parts or solution ready. Anyone know how this system is set up? Is it possible to source these sensors anywhere else? Any help would be greatly appreciated.