Nissan Altima GXE P0100 and stops at idle...does it

I have Nissan GXE 2001 bought on 2005 w/ 75000 miles on it at that time. It has almost 110000 miles now. I have regular oil change every 3 months. Regular tire rotation and wheel balance. I just had coolant pump replaced two months before. I am having new problem now. At one point, at a turning (at slow speed) the vehicle hesitated little bit and then I noticed the check engine light was on. Firestone told me it would cost 90 bucks to diagnosis the problem. I took car to Autozone and Advanced Auto. Both of them did a free check engine and gave me the Code P0100 - Mass air flow. Next day the car went off two times- one at red light and when waiting for turn. What could be the problem? Can Firestone fix this problem? And how much it could cost?
And the biggest question is does it worth to keep this car? I am spending $150-300 / every 3-4 months as Firestone mechanics recommends or tell everytime that there is somethind wrong.......
Please advise.posting.php?mode=post&f=1#

Check the wiring connections and harnesses for frayed wires and opens also a short going from the pcm to the Mass Air Flow and test the Mass Air Flow sensor it should read 5 volts with a 5 volt reference.

I would also check for a dirty or missing engine air filter. The slightest amount of dirt can really throw off the MAF reading. Instead of taking your car to the money pit, you really need to establish a good relationship with a reputable independent repair shop, preferably one that specializes in import cars. If you take it back to Firestone, they'll charge you 90.00 to read the code and then tell you it needs a MAF sensor.

Ferguson, You were right. Firestone charged me $90 for diagnosis. It was P0100 code which I already had before when I checked at Autozone and Advanced Auto for free. According to Firestone, they first checked any wire problems and they could not find any. They did the smoke test , resistant test and all seems ok. Then they checked the sensor and said it was sensor....they charged me $500 in total including diagnosis and replacement of sensor. They also told me that they gave me credit for the old sensor. If want to keep old sensor I have to pay $75.00.
The car is working fine after that and hope it will not give trouble.....I usually take car to firestone not because I like their job (not that bad either in my experience) but nearness to work. I can drop my car there and walk to work.

That sounds about right. I might add that if you want to hunt for a new place to get your car serviced, now is the time to do it, not when the vehicle is broke down. Good luck!!