replacing an O2 sensor is like changing a spark plug. You unplug the connector and unscrew it. IF your car is newer than 95, you'll need to have Zone erase the code after you done changing it. IF your car is 94-older, you can disconnect the battery while you change the sensor, and that will clear the code for you. Whatever you do, don't buy a Bosch brand sensor, they are absolute junk, buy a delco so you don't have to do it again in a month. To answer your question about the high voltage, I'll ty to explain. The o2 sensor creates voltage due to a chemical reaction with the exhaust gases. The amount of free oxygen in the exhaust varies depending on fuel/air mixture, and the o2 sensor tells the computer whether more or less fuel is needed by this voltage it creates. A bad o2 sensor will cause a drop in mileage, as well as an increase in emissions that will cause you to fail a cert test.