I did the job on my 1979 245DL some years back. Good things already said in this thread, maybe I can add a little.

Put the car up on ramps. Chock both rear wheels. Trans in neutral, e-brake on.

Cover the surface under the car with many layers of old newspapers. Remove the belly pan/gravel shield. Used whatever you want to clear away the road grit and solidified grease/crud/stuff around the bolts holding the lower motor mount brackets onto the crossmember. Don't poke too hard around p/s piping. Once that's cleaned off, take away the newspapers and the collected crud.

Remove the nuts on the lower ends of the bolts holding the RH motor mount to the crossmember. Then use the bottle jack with a 2x4x12 between it and the oil pan to lift the engine just a little, to take the weight off that RH motor mount. The bolts should slide out easily.

Then, from the topside, loosen the bolts holding the rubber part to the mount (you may want to pull the oil filter, too) and remove the bolts holding the upper bracket to the block.

You should be able to get the whole mount out now. Upper bracket, mount, lower bracket. Sitting in a comfortable place, put the brackets onto the new mount. Leave the nuts a little loose so you can wiggle things around to get the unit to go back in.

Put the unit in place, make the upper bracket bolts a snug finger tight. Go downstairs and lower the engine slowly. When you see everything lining up OK, slip in the lower bracket bolts. Go up and tighten the upper bracket bolts and the mount bolts, then tighten the lower bracket bolts.

The LH side is about the same. As I recall, I did not remove the upper bracket from the block on that side. Engine must lift higher to clear that way.

I did the job before I learned about usng vinyl gloves. Large cleanup time, lotsa GoJo outdoors, then much scrubbing the the kitchen sink.

Good Luck,

Bob

:>)