...and it is 38 pin, not 32.

Look here for location;

http://www.classic-roadster.de/cgi-bin/showitemlocation.cgi?TYPE=W140&X=8&Y=4&SORT=ITEM&START=&ITEM=X11%2F4

And Jims excellent page for more info on it;

http://pages.prodigy.net/jforgione/MB_X11.html

Remember that the electronics changed quite alot
on the W140 thru those years, and that what someone
has, maybe you donīt.

And to get this correct, here are a russian page with most of the
wiring diagrams for your car;

http://www.autolib.diakom.ru:8001/CAR/Mercedes-Benz/1995/S420/SYSTEM%20WIRING%20DIAGRAMS/

br,
syljua
W140 S320 1998 (german version with no OBDII connector, but with
OBDII signal in some of the 38 pins instead...)