If I remember right, I think you have to remove the lower bell housing section to gain access for the bolts that retain the torque converter to the tranny. I am refering to the OM603 six cylinder diesel, but I think the OM617 five cyl is the same.

Try this link, I think it will give you the info you are looking for. http://skinnerbox.steaky.org/service/library.html If you have trouble getting info for 123 bodies, try 124 body MBs.

BB