You'd need the bumper, fenders, hood, and headlights. I'm almost positive the core support can stay the same. If you were to buy it new thru ford it'd cost you atleast 1k for the parts alone, then paint would be an additional ~$500 unless you could get a hook up.
Unless you get it from a junkyard its not worth it.
I've been hoping to do the same thing... everything bolts right up. People have done 00 to 05 and 05 to 00. One guy had two red ones and swapped em over, he just said keep tract of what bolt goes with that piece and its easy as pie.
The only thing I could see being remotely challenging would be the headlight wiring.