500SEL Euro Front suspension

Please Help!! My 85 Euro spec 500SEL, the front end goes down and rests on the tires a couple of hours after you shut the engin off, and it takes 5 to 15 Min after you start the engin to come up to the normal level .

I priced the parts, about $1,200. plus labor. Is there any way of replacing the hydropneumatic front suspension with American spec springs, or any other ways of fixing it more reasonably. Thanks