How much should a dealer come down?

more than likely they wont. read the fine print. the dealer that has the car for 23959 has hidden costs such as on roads, financing and warranties. the dealer that has the car for 28888 more than likely has the costs included. talk to each dealer before hand and perhaps ask Ford beforehand aswell to find out more about the vehicle

Is the vehicle new? or a trade-in?

I purchased a new 2010 F-150 in August of 2010. The final price after everything was tacked on was 24G's. Keep in mind it was a work pot truck (plain old truck) for work. No frills, 6.5 foot bed. V8, cruise, radio, a/c. Definitely a work truck.

I just purchased a 2010XLT Supercrew, 5.5 bed, 5.4, chrome pkg, Tow pkg , 100K bumper to bumper Beautiful 27,500 out the door

You can try finding what it's worth here and see if you can find a better-priced truck in your area (or at least use the info as leverage): http://www.cargurus.com/Cars/l-Used-Ford-F-150- d337