Firstly, thank you everyone for your thoughtful words, it meant a lot in the first few days when I could hardly sleep and I replayed the accident in my head, thinking with dispair about my wrecked plans and material loss.
Now an update: I'm getting the truck back plus a settlement that covers all of the repairs, which I will take care of. They even covered the 12 gallons of diesel that leaked out of the tank plus an empty fuel can that flew in the wind and my RV deep cycle battery that jumped out of the box only to get flattened by an 18 wheeler :-).
It pays to fight for what's yours. I'm waiting for the official police report (this is Quebec :-( ) to see if I should sue the parts company for letting its drivers act at human missiles and wreck other people's lives. There is a law called "Duty to Care". Some people just have no clue what that means.