Front suspension strut air valve replacement

[pbmills]

On my S-430 (65000 mi.)The MB dealer wants to replace both front upper suspension strut valves due to leakage. 25,000 miles ago at 40,000 miles the same dealer replaced the the right front strut assembly and citing the repair order: "Found a leaking right front 220-320-24-38 Hydropneumatic 328565 strut assembly and replaced". They also mention the word Airmatic? The current dealer says the above mentioned valve(s) were different and were not replaced at that visit and are now leaking. My question is, how can I check if they really are leaking and how hard is to replace them. Phil has the valve kits and if they need replacing I would like to save myself $600 and do it myself if not too difficult.
I mean, how does one diagnose an air leak when they don't puddle up very much on the garage floor. PeterB

[mbdoc]

First you need to find out if the car has air-matic....standard on that car.

OR if the car is equipped with ABC (hydraulic) suspension.

[pbmills]

Yes they are airmatic part no: 328565 Pete

[pbmills]

How do I replace the strut valve once I get the kit?