Somehow, I seriously doubt the point of what he's doing is to save money...
Here's a link to a site that offers conversion kits. A lot of the cars they focus on are much smaller and lighter, but, if you strip down the benz, you might have something workable. Even if you got it to the point where it would get you 30-40 miles on a charge, that would be one cool commuter!
http://www.electroauto.com/gallery/vp914.shtml
Keep us posted on your progress Mistel and good for you for thinking in this direction, best of luck!