If the car can't make it 500 miles..... you haven't taken care of it very well. Sure, something can happen on any car but if you have a MB in good condition you have the RIGHT to take it on as long of a trip as you want. If it breaks down along the way, so be it.

There's something to be said for rental cars, that's for sure, but if you're afraid to drive your Mercedes on a 500 mile trip, you should sell the car.