welcome ik1 !!
For fuel leaks, first tighten all the hose clamps on your fuel lines.
for O rings, I would take the pump to a bearing place & try before you buy. it would be just your luck that for some reason MB had more than one size for different countries !
Good Luck with your car !

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving