Check Engine Light?

The light came off because the computer in the car has disabled the oxygen sensor. That means that your sensor still needs to be replaced the check engine light code is still stored in the computer. Until you get a new oxygen sensor then the code will be gone. Even if you disconnect the battery the code will be deleted for that moment. But once the computer tries to locate the oxygen sensor and reads that it is faulty then you'll have the check engine light back up again. Autozone and any other parts stores are not trying to cheat you. That price is right for a lot of oxygen sensors and the price depends on the type of car. Besides they read your code for free in which if you went to a garage they'll charge you a diagnostic fee around 80-120 dollars. Best of luck