Go to Harbor Freight
And get the breaker bar
Get the allen sockets
Check to see if they have the size you need. And really get into the breaker bar. They can really be stuck. MAKE SURE YOU RELEASE THE FILL PLUG FIRST. You don't want to drain everthing and then find out you can't fill it.
I could also recommend the 500 FtLb impact wrench they have, but do you have a compressor and would the impact wrench fit into the available space???
Also consider the breaker bar ( or allen wrench) and a piece of black pipe that will go over the BB/allen wrench that would extend the leverage and help you.
Again loosen the fill plug first
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