You will find lots of information on our forum, as Mike mentions below....
I replaced my distributor with the '123'. Even though the later aluminum distributors are not rebuildable, I did try this route at first, and was without luck.
So, my opinion is... if you have the later W113 with the aluminum distributor and you determine that it's no longer operational to your satisfaction, replace it with either a new Bosch aluminum distributor (very expensive), or with a '123' (still expensive, but less than the Bosch).
For those with the earlier W113 and the cast iron distributor, I recommend going the rebuild route. I think this is well worth the "try" and in keeping with the original setup.
Bob