The difficulty depends upon the equipment you have at hand. If you have a chain hoist of some kind, use a sling on the eyes found at the front and rear of the engine. This would be easiest. If not, a floor jack and a two by twelve block under the pan to distribute the weight should work.
There are two allen bolts that go up through the bottom. Remove them, raise the engine far enough to change the mounts. To be on the safe side you may want to disconnect the radiator hoses and throttle linkage. I believe the exhaust and other things will be okay if you raise the engine only high enough to get the mount out and back in.
I would expect Deezel to chime in here with safety tips. You may know that he is our self appointed Safety Officer on this site. And I'm sure we all appreciate it. He has offered some VERY GOOD safety points in the past.
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in