Mercedes Benz Club of Russia maintains an Illustrated (updating as MB does)
Electronic Parts Catalog.
Both before and after 9/2000
http://www.detali.ru/cat/oem_mb1.asp?TP=1&F=163154&VIN=
This is the Before link:
http://www.detali.ru/cat/oem_mb1.asp?TP=1&F=163154_04S&M=112.942&GA=722.662&
The fuel filter location is the same on both.
Maybe you can figure out from the pictograms where it is?
(Looks to be about 2 feet forward of the Gasoline Fill and under the Chassis.)
As you can see it's #9.