I have found that the local shock places think it is cool to charge $600 to do all 4, no alignment but just parts and labor. According the MB you only have about 3 bolts to take out and jack the car up and put the new one in. I have found em online for about $75.40 for the Heavy Duty and $70ish for the comfort here:

http://www.eshocks.com/bil_veh3.asp?Model_Index=198&Make=Mercedes&Group1=Cars&Make_Long=Mercedes&Manf=Bilstein

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1980 300D European
"The Red Fox"
200,000 miles

2003 Chevrolet Silverado

609 Certification