Make sure you check the oil at EVERY fill-up, and plan on having the oil changed every 3,000 miles.

I would buy about three oil filters before you go. I have found that any Quickie Lube place will have oil for Diesel engines but few have oil filters for a 240D or any other older Mercedes. If you provide your own filter they will usually knock a few buchs off the price of the oil change as well.

I would also buy a new tire for the spare, a flashlight just for the car and a package of flashlight batteries.

Keep us posted on how the trip is going. I would be interested in MPG figures and I bet others would, too.