Sounds like you already realize the way this is going to go; The insurance company WILL total this truck. It may be completely fixable, but they are all about the bottom line and they have no emotional attachment to this truck the way you do. I've been through this type of thing before, and if it goes for you the same as it did for me just be prepared to receive a low-ball settlement offer from the insurance company. I know you said your dad is an insurance agent, so you have his advice to lean on throughout this process. I'm guessing that they will hit you at the knees with their first offer, so just realize that this is what they are trained to do. Most people won't argue with them and they will just accept their first settlement offer. The insurance company obviously will try to get out of it as cheaply as they can. They will check online for similar trucks and what they are selling for, which probably won't even compare to the actual condition/value of your truck, and that is where they will get a value for your truck. Just try and get them to offer a better deal. I know in my case, and after some back and forth, I got a better deal and I got to keep my vehicle without paying anything to do so.
If it is the same everywhere else, before you will receive any kind of settlement check from the insurance company after they consider it totaled, you will first have to title the truck as being salvaged. If that is the case where you live, check and see what the requirements are to go from a salvage to a reconstructed title.
I live in Pennsylvania, so I'm not familiar with how things are in other states, but here once a vehicle has been filed as being salvaged, then it will have to be 100% correctly repaired and then go through a lengthy inspection process by a specially licensed garage for reconstructed vehicles (NOT Bob's Auto down on the corner with his state inspection license). You have to show where all of the parts were sourced from, and things have to be exactly as the factory would have had them before they will issue it a reconstructed title. Basically, if you modified anything from how it left the factory, it will have to be undone before a reconstructed title will be issued.
I don't know if the things I mentioned will come into play where you live, but I just wanted to mention it just in case.
Good luck to you!