The sensor most likely is the cause of your idle speed problem.  It is part
of the ciruitry that controls the mixture and throttle.  

Before spending that much to replace it, you could try cleaning the sensor.  
It should be mounted in the tube from the air filter to the throttle body.

Some owners in a different car make group that I used to read would clean
their's at least monthly.

I agree with Jeff. A cleaning of the sensor would be the first thing
to try. A can of electrical contact cleaner is much cheaper than a new
MAF. Don't use other types of cleaners or for sure you will be on the
hook for a new MAF. Usually the MAF consists of a wire that is heated.
The airflow passing it will affect it and the vehicle can measure the
change in the wire. If there is dirt build-up on the wire then it will
heat/cool improperly so the vehicle can't get a proper reading and
hence give you the problems you are experiencing.

Cheers,
Lawrence