02 sensor

I have a 2000 toyota tacoma with 247, 000 on it. The engine light came on, and since I needed to take it into the Toyota dealer for a lube and general maintance, I asked them to do a diagnostic on it. They called and it is the 02 sensor. It is some $300 and odd numbers to get it fixed. What exactly is the 02 sensor? Thanks and would you recommend me getting this fixed?

Yes it needs to be fixed. It affects fuel mixture. If you are mechanically inclined, you can fix it yourself. The O2 sensor is located in the exhaust system close to the catalytic converter. The O2 sensor may not be a dealer only part, so shop around. For future reference, Autozone will read codes for free.