I have 95 contour. Check engine light goes on intermittently and car seems like it lacks power in terms of acceleration. A mechanic told me that my fuel mix is "light" and that I may need new O2 sensor. In 95 model there is only 1 O2 sensor. is it likely that it is O2 sensor? Is the O2 sensor on exhaust and approximately how far from the front of the exhaust system is it located. Is it something I can do myself? I have 130,000 km on my car.

Thanks..