ohh its not hard, i think the size is either 13 or 12? can't remember exactally but just get the wrench set out and find the right size, just loosen it and pull it out of ur exhaust manifold. If it looks black on the top then the carbon has gotten to it and u need to replace it. if it isn't black on top and just gold, then it should be fine, u can always just check the connections. If it hasn't ever been replaced then its probably that its bad. if its bad, follow the wires and it should disconnect from a pull out area that goes to ur firewall. ok, so if its broken what u do, is disconnect it and go to a place like Autozone, get the Bosch Universal O2 sensor, it works the same but with half the price
after tahts done, just cut the old wire off your old 02 sensor so u can reconnect it and then strip the wire, and tie the 2 wires together and cover with electrical tape, then replug it in and wrench it back into ur exhaust manifold.
Now, if u can't find it anywhere, it should be real easy. its on ur exhaust manifold, mine was under the 6th cylinder spark plug near the back when it goes under the firewall of ur engine bay. just search through it(if u feel with ur hands, make sure its not hot
) but anyways, u'll see a little pole like thing poking out of the Exhaust manifold, that'll be ur O2 sensor. SOME cars have more then one, but i doubt u will. if u have any other questions lemme know!