I rebuilt my 240 D engine also in an 83 240 D.
If you can rebuild one--no one will be able to tune it better than you can--check the manual for the procedure--if u dont have it email me rtc9@home.com and I'll fax it to you. If you can build it, no one will fix it better than you.
I'll bet the next time you are at MB dealer picking up pats you will feel smug watching customers pick up thier cars and paying hier repair bills!