major engine problems...help!

My 99 Grand am (3.4L) is having major problems. As I was getting off of the expressway engine started to misfire and the Service Engine Soon light started flashing. the stutter continued to get worse and by the time I found a place to park my car, it started to over heat. I got it towed home. I took it to Meineke to have it scanned and the following trouble codes came up.

P0300 Engine Misfire Detected
P0463 Fuel Level sensor high voltage
P1111 Intake air temperature (IAT) sensor circuit intermittant high voltage

I was hoping that the ignition coils went bad but it doesn't seem to be the case. Meineke says it is possibly a cylinder head problem.

Does anyone have any ideas or suggestions as to what my next move should be? I am pretty handy but I am not a mechanic and I have no idea how to replace head gaskets. nor do I want to pour $1500 into this car!

Help

your engine misfire is common with GAs. Either caused by the fuel injectors being dirty/clogged or your plugs & wires are bad.
It alone will cause the engine to run Very poorly, and hav little or no power at times.

The fuel level code could be your fuel level device is bad, another common prob with GAs.
IAT-Intake air temp ,, could be bad or hav broken wire(s).

Did Meineke clear those trouble codes?
And did they come back, making it run rough/bad/overheating again?

I would NOT think its a headgasket, at least from what you hav metioned.

When you say it started overheating, how hot did it really get?
Over 230deg?
Are you loosing coolant anywhere?
A simple compression test on each cylinder can be very reliable identiying a headgasket problem.