The best way to purchase MAF sensor is to cross-check OE numbers found on the old unit (under the hood look at the MAF's housing and read engraved numbers) and compare with the numbers presented with the MAF's description. Sometimes the problem may not be necessarily directly related to the malfunctioning MAF, just get your car scanned by the OBDII tool which is available at most garages. There are plenty of sources where you could buy MAF sensors online. Before purchasing make sure you are getting the correct part.
Note: A mass airflow sensor is used to find out the mass of air entering a fuel-injected engine. The air mass information is necessary for the engine control unit (ECU) to balance and deliver the correct fuel mass to the engine. The sensing element in MAF sensors can be easily contaminated causing hard starting, rough idle, hesitation and stalling problems.
No software re-program of the vehicle's computer is required for the MAF sensor replacement. Easy do-it-yourself installation task.

I hope this information will be useful for you and you'll resolve the problem with your car.