Hello and welcome to Just answer.com, Super mechanic here. About your vehicle.
You will want to take the struts out to get the mounts replaced. Here is what the data base has for that.
300CE, D, E, SD, SL & TE & 1992 300SE, EXCEPT 300E & TE w/4MATIC The damper struts are simultaneously serving as deflection stops for the front wheels. Loosen damper strut attaching nuts and bolts only with vehicle wheels contacting floor.
Yes, the upper strut mount, (bearing, support) is at the top and goes through the body. The strut would have to come out to do that. Number 10 in the diagram?
Well, the part numbers will sometimes be different. Does it look like the #10 in the diagram? A hole in the center and a bearing?