2002 Rendezvous Misfire

Yesterday morining I got in my car and it started to misfire. I took it to Auto Zone for hook up on their diagnostic. Result was as anticipated, "Misfire Cylinder 3". I changed the plugs and wires, no help. I changed the coil, no help. I dumped in some "Lucas" injector cleaner, no help (yet). What is my next step? Do I give it time to see if the injector opens up? Do I just go ahead and replace injector #3? Or do I pray to the car gods that I don't have a cracked head? Please help!