Just do yourself a favor and clean the MAF before you go run out and buy a code scanner. I've had my CEL come on about 5 times or so, and everytime it said it was an O2 sensor, I just cleaned the MAF and it was good for another 6 months before it happened again.

The MAF gets dirty and throws the computer all whack. Use a quick dry electrical parts cleaning spray. Douse the thing. Plug it back in, have the light reset at autozone, drive away. If it comes back on soon after being reset, then you might have a bigger problem.

My 2 cents.