Toyota Repair: air fuel ratio sensor, air fuel ratio, fuel mileage

Question
My Toyota dealer says I need an A/F sensor.  He says that if I don't install a new one,  I would use more gas.  Can you tell me how much more gas and will it do harm if I don't replace it?  $485.00 is tough to come by these days.
THANX for your assistance.

Answer
The difference in fuel mileage would be minimal,if nay at all, have them clear the code or you can try do do it yourself by disconnecting the battery for ten seconds, the light should stay off for a while. By the way, there are aftermarket sensors available at most autoparts stores and you may also consider a used one from a salvage yard.