If you are good with a wrench and have some simple tools you can fix it. If not just about any tech can put on an O2. This is not a big deal. You will not pass an emissions test right now, but no damage is being done to the car---you are okay. What is happening is the O2 is not sending the correct voltage (approx 5 volts) back to the ECM (car's main computer) so the ECM is going to the rich side just to be safe. Rich waste fuel, but lean will burn valves and then some---so rich is best when the ECM does not get the data it needs. Do get it fix though because if you leave the light on and have another problem you will not know.