My "check engine" light came on; took the car to my mechanic, who read the code. Apparently the "front oxygen sensor" is what tripped the code. He said I need not worry about the sensor until the light goes on again, and that would be the time to think about replacement. Is this a vital part (what doe it do)? Also, how difficult is this as a do-it-yourself job? (I do brakes, oil changes, and similar minor maint., and don't wnat to bite off more than I can chew).
Thanks