I would not allow the insurance company to have the truck repaired ... only accept a total loss. Anything else will be a problem down the road. Fire damage is very bad and can't always be seen until its too late. I've seen examples of twisted frames, deformed insulation on wiring, etc.
Second, I would start making a list of the items contained in the truck, you'll need a description and value of items to claim a loss. Home owners or some renters insurance may help cover some costs if the vehicle insurance is lacking. Anything not covered may be claimed as a loss on taxes for 2018. Sorry for you loss, glad to see no one was hurt.