There were a couple of posts a while back regarding the conversion from auto to manual transmissions. The general consensus was that it can be done but is likely time consuming. It may be cheaper to sell what you have and buy a suitable W124 5 speed. Are you better off taking you car and converting it for $5000 or selling it and putting $5000 more into an authentic 5 speed. If you are experienced with mechanics it helps. Having a donor car is a big help. Your car will be out of action for some time. One fellow said that he did it and that it was easy. Of course, another guy did an amazing sway of a Buick V6 into a 300D and he said it was easy too. (It doesn't look easy to me.) Good luck with what ever you decide to do.