Nurse-
There should be a black rubber hollow "quarter round" aircraft style weatherstrip glued to inside of door that makes contact with frame and provides seal against water and wind... Is that still there? Did prior owner possible replace with some other form of weatherstripping that doesn't seal completely? It is rarely sold in hardware or home supply stores...
One source is Aircraft Spruce and Specialty (
http://www.aircraftspruce.com/menus/ap/doorseal.html ) which supplies parts for airplanes...
Hinge pins rising are not uncommon, and result from loosening after original installation including tap from bottom with punch to expand lower section and hold in place. Dealer could fix that relatively inexpensively as well, and will have ability to order weatherstripping from Airstream directly. Not sure wheterh more expensive from Aircraft places or Airstream, but it costs $$ per foot, not pennies...
John McG