I would not doubt the Wa DOL would be a PITA! Even with my IHC that is COMMERCIAL, they can get picky. I was needing a DOT number if over 26K IIRC, and/or a trailer over 10K and going across state lines......maybe they have changed in the last few months. I guess I will find out in October.
Insurance should not be an issue, about the same as a 3500. Maybe a few bucks more. As the liability goes up, but comp and collision go down some. Altho the down does not quite make up for the up!
At 12K and over gvw is a hit, as they throw in some $75 DOT something or other, but before and after this, all of about 10 bucks per ton increase.
marty