Sorry to hear about your tire mishap.
As for the suspicion of a cracked head, replacing a plug again after it had just been replaced (presumably) is not going to do anything. However, 'reading' that plug may tell you if there is anything untoward happening in that cylinder. I would agree with the two posters that the 'mechanic' who took your laptop and your camcorder also took you for a ride... There are many possible reasons for a misfire, bad injector, bad coil (though that would affect two cylinders on opposite sides of the engine), etc, etc.
Sorry, I am way too far from Plano to come and help you. If you have someone more-or-less competent coming and bringing even a simple scanner, they should run on-demand diagnostics and see what else shows up and if that 301 code even persists. The (presumably) competent guy should follow the list of possible causes (any manual has that), and if nothing external shows up, the suspicion is on base engine. Checking compression - at least on the passenger side - is a simple thing to do. If your coolant level is going down and you don't see an external leak, look for signs of coolant in the oil (odor, milky appearance). Also check if you can see any signs of oil floating on top of the coolant in the burp bottle. Pressure-testing the cooling system is probably in order too. You can rent a compression gauge and a pressure-tester (and some other tools) for free from places like Autozone or O'Reilly. Good Luck!