2004 Ford Station Wagon

Engine Mechanical problem
2004 Ford Station Wagon 6 cyl Front Wheel Drive Automatic 131000 miles

Hello, when we left for church Sunday my car felt like it was running a little rough, I have NEVER had problems out of my car so the way it was running caught everyone's attention. As I pulled out of the driveway and accelerated my car started feeling like it was missing, once I hit 20 it started bogging down. I stopped turned off the car and started again. This time it did a little better at first, but once I got up to 20 again it did the same thing for a second then I felt it kinda kick, then it started running better, not great, but better. I returned to the house and later went back out about 2 hours later and tried again. The car ran alot better then. It felt like it was having troubles at first but didn't act nearly as bad. I was able to accelerate fine, but then the engine light came on. I have been told it may just be bad gasoline or the spark plugs. Can you please tell me what to check?
I bought this car as a certified pre-owned vehicle and purchased an extended warranty on it. I am not sure if it is still covered but if so should I take it to Ford dealership or a regular shop if I need maintenance?

Thank you for any help you can give me
November 16, 2009.

Did the check engine light come on? Has fuel pressure been checked?

As far as the warranty, it you purchased it at a dealer, I would take it there if still valid.

Let me know.