1991 300CE

Here is what I did:

1) Release shroud surrounding fan. When you raise the motor, the fan blades will go well above the shroud. On this car, just twist off the ring part of the shroud and rest on fan blades.

2) Put front wheels on ramps. Chock rear wheels.

3) Work on the left upper bolt first. If you can't get this one, no sense in doing anything else.

a) Do it like porkface mentioned.

b) I threaded a long 1/4" extension down in a gap in the intake manifold, just behind the EHA. It is pretty much a straight shot if you are in the right hole. Have someone hold the extension, while you are below attaching it to a 17mm flex socket. A universal and regular 17mm socket may work. Be careful here as there is a lot of delicate linkage around. Make sure you are on the bolt solid and break it loose.

c) I used this method on a Lexus LS400. Put stubby 17mm box end of wrench on the bolt.
Use the female end of a long 3/8" extension on one of the tines on the open end of the stubby and give it a good pop with a rubber mallet.

4) Remove 8mm allen bolt under each mount. Right upper bolt is easy.

5) Raise motor with piece of wood under oil pan. Watch the motor as you raise it. Initially the motor won't move as you take up the slack in the suspension. Raise, check to see if you can pull out the old mount, raise, check, etc. You'll need to raise it a bit more to get a new full sized mount in.