I need to change the vaccum pump on our 1987 190d, how big of a job am I looking at. Should I have my mechanic do it?

I found it simple to do on the larger body (W126) car. May have removed the belt for access. Do not know access on your car. Before starting establish: How to oil it, if desired. Which gasket to use. Remove or use basket, if present. When bolting it on, consider having the radial cam positioned so the arm is down, reducing mounting pressure.

Search "603 vac pump change" for some answers.