Depending on what the dealer repair paperwork states, the norm from GM is an even up trade model for model, option for option, replacement MSRP VS MSRP + or - numbers. There's a minus of cents per mile of use on the odometer levied just like mileage cost per mile on a lease contract that will be your responsibility. Pay for the miles of use!
No, they aren't going to give you a new truck with zero miles on it and trade even up for your present truck which has X miles of driving use because you have the $$$ responsibility for normal miles driven shown on your odometer. Remember that you have had the use of the truck for about 3 years now and GM nor any manufacturer will reimburse you for that use. That's only fair and the way it should be.
Some states will collect the sales tax amount on the new vehicle and some won't. Some only collect the difference in the present market value between the 2 trucks. You pay for the title and the plate/registration transfer just as if you'd purchased the new truck. Not the manufacturer or dealer's responsibility.
You actually come out way ahead as you will now have a 3 year newer truck apples for apples to your present truck unless you choose to upgrade to a higher trim level or a more optioned out truck or a larger model (Ie - DRW vs SRW). You will pay that difference in cost.
Lots of variables can or will apply so there's no set $ amount that will be the final cost until such re-purchase actually takes place which gives you so many options of choice and choices. The final cost from GM or the dealer will not pay for the state charges but it will show on the final paperwork so you know the amount.
The above is in general how it usually works as there's no way all the details/variables are known at this point.