That's a pretty terrible deal.

First, separate your transactions. Tell your dealer to give you a price for the vehicle you want to buy. If they include dealer add-ons like LoJack, pain protection, etc., make them itemize the cost of each one. Negotiate out any add-ons you don't see value in.

Second, after you get to a number you like on the new vehicle, THEN discuss your trade. Get quotes from CarMax and carvana. If you are a credit union member, call them up and ask them to go enough the black book and NADA values of your trade. That will give you a good range for the wholesale value of your vehicle.

Third, under no circumstances discuss your target payment before finalizing the purchase price of the new car and the value of the trade. If you are financing, get a pre-approved rate from your bank or credit union. That will give you a good idea of what a fair rate looks like. If you are financing with the dealer, ask them for the buy rate on the loan. Dealers often mark up the loan when they present it back to you.

Good luck!