IIRC
Wash the top with water from a hose to remove lose material.
Use a mild soap and a soft brush to clean the top. Every year, Mercedes says, you apply a silicon spray material on the fabric to keep it water proof. The dealer can get the spray silicon. I'm not sure what the number is since I have not done it to my car yet. I should, I've had it 8 years and would say its past due.
I think this is all that I read when I was lookin this up.
It was in my SL owners manual I think.

Dave

PS a great looking car. I would love to own one. I talked to a 52 owner here in DFW and was suprised to find out that the frame in that year was made out of wood. He explained how he had to rebuild the frame in his restoration.

__________________
1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car