You raise the engine before tackling the upper bolts - creates lots more room to work. Here's my routine, slightly modified from my E420 notes:

Remove fan shroud – 3 8mm bolts, 2 clips (E420)
Raise all 4 tires on 6 inch blocks or ramps
Remove lower MM bolts – 13mm, 8" extension
Jack up engine at pan
Remove top bolts, 17mm (lever on wrench from top)
Remove MM/shields / install new MM
Install lower bolts loosely, with blue loctite
Lower engine partially until top bolts can be installed
Lower engine more – tighten top and bottom bolts
Lower engine all the way
Tighten upper bolts to 40 ft. lbs. (E420)
Tighten lower bolts to 18 ft lbs (E420)
Re-secure fan shroud

The reason I raise all four wheels to start is because it makes the engine lift less exciting. If you raise only the front wheels on blocks/ramps, and then jack the engine it creates quite an angle for the jack under the oil pan. Flatter seems safer.

Remember some of this is 420 specific. On the 420 driver side you have to remove a piece of exhaust pipe to get the mount out of the engine compartment.