I won't (can't off the top of my head) explain all the ins/outs of smartkeys. But your car came with 2 smartkeys and one somewhat limited function valet smartkey (it will start the car). If you are down to one smartkey you have to use a MB dealer for an extra key (very common). I have never heard of this taking 30 days. The most common (universal) scenario is 2-3 working days. You will need to show the dealer a vehicle registration with your name on it for the car (proves your the right guy getting the key) and a drivers license. They can be as high as $200 dollars or more. MB dealer key prices do vary, I got a new smartkey w/steel key insert from MB Carlsbad a year ago for $145.Personally I would resist paying $200 plus and shop it a bit. 30 days has got to be incorrect as all smartkeys in USA come from the same place (Texas, I think), and no MBUSA dealer would take all that time.
Good luck,
Paul
98 E300