My 05, 3.5 liter will not start. It turns over quickly enough, and tries to fire, but will not run. I charged the battery, then replaced it with a new battery I had here. All the dome lights, panel lights, parking lights will work, but the headlights will not.

 

If it turns over the problem is not the battery. It's either fuel or the ignition system. If the headlights are out I'd guess there an electrical problem. Start by checking the fuses and relays.