O2 Sensor

My check eng. light has been on for abt 3 months. My 2003 corolla LE has only 35K miles (I bought certified used w/12K on engine) - the dealer determined bad O2 sensor, but now want $230 just for the part and another $175 for labor. Is this reasonable for a car of this mileage? Should I take it somewhere else? There is definitely lower mpg and strong gas smell (but seems like the mpg has always been lower than the advertised # and the smell, although worse now, has always been there a little). Any thoughts? I called Toyota cust. svc. and of course, they take no responsibility for possible faulty unit. Do I have any resource, or do I just have a lemon and should I get rid of it before something else goes?

I would start by checking around locally to see what other local shops are charging for the work. You local prices are likely different than mine. So I can’t say what a good price would be in your area. Stay away from chain places. Local independent shops are usually the best bet.

It would be a good idea to get the actual error code. It should be like “P1234”

I would also consider figuring out what maintenance is now due or over due for your car.