I've never had a hard time finding diesel as backwater hicks drive diesel trucks That and when you get ~550 miles per tank as long as you plan/think ahead you shouldnt have any issues.
I personally think AWD is required but I trek to CAN, MT, WY a few times each winter. Kinda depends on your winter intent.
Diesel pricing is a funtion of some current federal and state regulations... I dont know about WA but you get a large tax write off in Oregon for buying Biodiesel. But yeah: who knows... write your congress person.
Semi related and some food for thought: I believe some local govenors are looking into ditching a portion of the gas tax and replacing it with a tax per mile... this might alter your ROI analysis
And suby is suppose to have a diesel offering soon (or is it already out?)
And... look for a diesel hybrid sometime soon from VW... 100+ mpg!