I don't have the same year and model but in the thread below is what I did. As mentioned in that thread there is also an older thread that I saw.
Don't know if your U-joint would be the same size or not. From what research I did the U-joint on my 84 /w123 300D is the same as the one that goes backwards to the 1960's. Mercedes kept the same part.
The short story is I changed the U-joint on mine and hit as served me since that time.
I answered a similar post over on benzworld and I looked up the cost of the same U-joint I used, and they are around $30
http://www.peachparts.com/shopforum/diesel-discussion/293976-drive-shaft-u-joint-staked-crimped-place-now-what-do.html
It is unfortunate that there is no tool set to do this job. Instead of grinding off the stakes which in theory should change the balance what is needed is a swaging tool that squashes the staked metal bac into place or at least most of the metal. If that was possible it would preserve the balance.
There is another tool called a burnishing tool that has multiple rollers that expands and also would do the same to form the metal back to where it came from.