No trade is good. If this is the truck you want, plug in all the information in KBB (Kelly Blue Book) and NADA as well. You did not state the mileage on the truck. I did a quick look on KBB for my area San Diego County and inputted the basic info for that truck (4X4, sport, and I used 48k for miles). KBB came back at $19,500 for excellent trade in, $21,955 for excellent private party sale. Use the auto trader
and look for like vehicles in the area as a comparison for price. Maybe there is another vehicle that you may like while you are searching. There is no telling what the dealer purchased (bought at auction or was it a trade) the truck for and how much they have invested in it. I can tell you that here in San Diego County that vehicle would have a price of $24K. I just saw a 2007 4X4 at Carmax for that price. Only you can decide if the vehicle is worth the price.
Never shop for a vehicle by payment always by price. A classic line from the dealer is "How much can you afford a month". It appears you are going to use a co-signer to purchase this vehicle. Depending upon the credit score of the co-signer is going to determine the interest rate at which the loan will be financed at. The higher the credit score the lower the interest rate you will qualify for. The higher the interest rate the higher the payment will be a month. To give you an example, I am a member of Navy Federal Credit Union and there current interest rates for a that vehicle is: up to 36 months at 3.59%, and 37 to 60 months is 3.99%.
I would recommend not buying any additional services or options ( car alarm, window tinting, extended warranty, undercoating) at the dealer. They are grossly marked up. I have a 2008 Tacoma that I purchased new and they wanted over $2K for the extended warranty for 8yrs and 125K miles. I bought the same warranty from another Toyota dealership out of state via the internet for $1,399.00.