Dodge: O2 Sensor, dodge ram 1500, horrible gas

Question
My husband owns a 2001 dodge ram 1500 quad cab. It's been idling and running really rough and getting horrible gas milage (worse than normal) :). He had it into the shop and they thought it might be an O2 sensor. Is there a way that he can replace them himself? Or maybe clean them? We hate having to pay costly labor fees, so if he can do it himself that would be great. Do you have any tips. Thank you.

Answer
Yes you can replace them,they are under the truck on the exhaust pipe either in catalytic converter or in fron of it or behind converter,they screw in and out.More than likely the engine light would be on but you can try it.Also would have the catalytic converter checked,it can also cause this.