I went to Alaska in my 240D in 1999. Was a great trip. Rev the engine like you stole it but make sure you have nice clean oil every 5000 miles. Consider bringing a filter with you for the change up there.
Only trouble I had was an alternator that went bad - the mounts got all oval and the belt wouldn't hold tension. NAPA in Anchorage sold me a Delco alternator that worked great for several years until I sold the car.
Contrary to poplular belief, the roads up there are pretty good. I recall only having to drive 100 or so miles on gravel plus several hundred more (by choice) on the Dalton highway.
From the driver's seat:
http://homepage.mac.com/grozier/resources/100mph.html
Ted