Yes, it's free for those 3 services, these are referred to as the "Sign and Drive" services. Even if you are too far away from a dealership (most dealers agree to a 30 mile radius as their service area) MB will STILL pay for an alternate service provider to help you, although don't expct the same level of competence as a dealer tech.
The roadside assistance doesn't expire, and it stays with the vehicle, doesn't matter if you're the first owner or not.

http://www.mbusa.com/brand/container.jsp?/care/clientcare/roadside_assistance.jsp

Gilly

ps They won't charge you for the 2 or 3 gallons of gas (or Diesel) they will bring out to you. If you runout of Diesel, I'd stress this a few times when talking to Roadside Assistance about your dilema, especially at 2 am .