In a previous posting I wrote about our adventure with a failing vacuum pump on a 1996 E300.

It took all day to learn the part number on the timing gear that runs the pump. The local Mercedes dealer could not find the part or number and after searching the net for too long finally called the Mercedes-Benz Classic Center. They call the part Injection timing device part number 605 070 06 45
None exist in the USA and just a handful in Germany, may get it next week.

The question is: What is the R&R procedure of the Timing gear? As it also controls the injection timing, am I in danger of throwing off the timing?
And can the job be done through the existing hole where the vacuum pump goes of do I need to remove the head?

Thanks for your consideration.