2000 Sunfire GT O2 Sensor

Hi,
My check engine light came on so naturally i had my car checked out, and they told me my rear or sensor (sensor #2) is shot, and i was quoted $300 plus tax. Anyway i went to a smaller repair guy and he wants $150 plus tax, and he's a GM mechanic too, but that's not the issue. now the check engine light has gone out, so i checked my owners manual to see if the light would naturally go out after awhile, i didn't think it would, and the manual doesn't say that it should. But it does say that if oyu have just gone thru lots of water the light may come on cuz your electric parts r wet, and the connections could be loose or whatever, and where i live it had rained for like a week straight. So my question is; Could the sensor just have been wet, or should I get it replaced anyway? any advice would be great. Thanks

I've never had to replace the 02 sensor on my car, so someone can correct me on my next statement. But, I wouldn't imagine the sensor costing any more that $15-$20. As far as the actual sensor, it's just a matter of unbolting and hooking up a new wire and you're set. Nothing but a 5 minute job, 10 if you gotta get the car jacked up.