The fact that the OPP said it's likely a write-off, and that it's a '93 would have me thinking yes, it'll be written off. To get the most replacement money though, you need to arm yourself with some information, because I'd expect a pretty low amount from your insurance company.
You want to approach it like this: "What can I buy a '93 GMC 4x4 with xxx,xxx kms on it, and x,y,z equipment, and in the same condition as mine was?"
Look for all the ads you can find where people are SELLING vehicles like yours, so that you can sya to the insurance company "If I want to replace my truck, here's what it's realistically going to cost me".
When my sister's van was written off, she got lowballed as expected. She offered to fax them all of the ads she had found where vans like hers were selling for more than what the ins. co had offered, and they upped the amount.
Just my $0.02. Glad you and your family are ok...hope it works out as well as possible for you.