Because you have positive equity in the vehicle, the dealer will offer trade-in value for it. Then, they’ll either take that money and cut you a check (which is getting less popular) or they will pay off your loan. If they pay off the loan, you could potentially get the leftover proceeds.
When you have positive equity and you trade in your vehicle, car dealerships will try to hustle you a bit to add optional features (like tinted windows) to your new F-250. However, this money would be better used as a down payment or as the initial investment in an emergency fund.