Transmission, Diff, Power steering, radiator fluids....
#2
do a search, each is different
it's in your owners manual maintenance supplement
do a search, it's been posted here also, many threads on it
it's usually a mileage and at least so many years if mileage not reached
not sure steering is on the list
#3
here's the manuals http://www.mbusa.com/mercedes/servic...enance_manuals