coil pack question

Having been through this before, I can give you some pointers about what to try. It might be the coil pack, or it might be a plug or a plug wire. If you want to eliminate the plugs and wires, you can try swapping them two at a time to see if the misfire moves with them (you'll have to get the code read each time to see which cylinder is misfiring). Or, if it's time you can just replace all the plugs and get a new wire set. It's still cheaper than a coil pack! Did the auto store say that there were multiple cylinders misfiring, or just one misfiring a lot?

If the misfire doesn't move, then it looks like you'll be getting another coil pack. They're about $80 online, and probably about $250 at the Ford dealer. Replacing it yourself is really easy- it's right on top of the engine and there are just a few fasteners to unscrew. Just make sure you don't mix up the wires- transfer one at a time to prevent that.

You shouldn't drive the car too much with that condition, but it won't kill it to drive it to the auto store and back. Once it's fixed, you might want to get the oil changed since the unburned fuel from the misfiring cylinder might have been washing down the walls into the oil, diluting it.