P0057 o2 sensor out should i fix before next inspection
 

One of my o2 sensors is out . check engine light is on along with blinkin traction control light. I went and got it checked out at Autozone P0057 code. Will this effect my cars performance and mpg. Im lookin to wait month or two til I can save up enoug to fix it however if it is something that will affect my cars performance and gas mileage ill do it sooner.

I found a guy on craiglists said he would fix it for 300. Dealership wanted 380. IS thisa difficult sensor to get to. Ive read you had to remove passenger seat to get to the wires

Thanks for the help guys