I came across this tonight... 4 hour DVD rebuilding the OM617 turbo diesel. $79.98.
No affiliation.
http://www.benzproducts.com/benzproducts_main_page_002.htm
This is a sample video from the DVD:
http://www.benzproducts.com/benzproducts_main_page_007.htm
It is not specific to the W115, but we can add it to the list of resources of reference materials. It may be helpful to someone.
A bit pricey..... Has anyone used it?