Is it hard to replace a door in a 2003 Mercedes ML 350?

I planned on just purchasing a door from a junk yard in the same color as my car and swapping it out. I know there are electronics and an airbag in the door. I have to replace at least the rear passenger door, but I also have to replace the front passenger side door sooner or later also.

not that hard if you have mechanical sense. you must removed all the harness from the door, lining up the door to shut right will be the tough part.

I may be wrong, but I don't think it is as simple as "swapping" doors.
I bet something won't work or fit if you have a new completely assembled door. If I had a door from a junk yard, I'd still take it to a good body shop to install. This way you save money on parts and have professional installation.
On the other hand, what do you must loose, except a day of work, if you try?