2002 Ford Focus my car stalls at idle

In about april 2008, my car started sputting while at a red light. I gave it a month or so and then my check engine light came on. My car now hesitates and jumps while in idle and sometimes even dies. My dad has changed all my spark plugs and etc. He also purchased a brand new alternator for my car. We have flushed the gas tank and everything else my dad could think of. Now he thinks it could be my o2 sensors. Before we spend anymore money on this vehicle im wondering if you could give me any advice or even point me to the right direction of what could possibly be wrong with my car. Its only an 02' and it doesnt even have 50,000 miles yet. I dont think my car should be having the kinds of problems it has been. Any advice would be helpful. Thank you