Many thanks to Dan, Beo, Safado and Jomama. Did the O2 sensor replacement yesterday. Took me less than an hour and I DON'T wrench at all. Truck runs much smoother now as well. A little Liquid Wrench about 20 minutes before starting and the four bolts came off very easily. Had more trouble with the damn connectors than access to the bolts. Superior services Dan! Thanks!