I have to agree with refusing "Politely" their first offer. I also agree on getting an assement of it's actual value. It's an inexpensive way to get what it's really worth. Ins companies are about making money, but they still have to follow rules. You just have to show them your serious. Then if that doesn't work, Release the Hounds! (Lawyers)
Once that is done, You can also pick up another like year truck, and transfer all your good stuff to that frame. You can usually find rigs with bad bodies for cheap that still have reasonable frames. It's a bit of work, but if you love the rig, it's worth it. It also gives you a chance to do some frame/suspension mods or just making it look better with a little paint here and there. You could probably do it with the ins money and still come out ahead. Not to mention selling any extra parts.
However it turns out, It sucks losing an old friend to someone's carelessness or stupidity.
Good Luck!