Sorry for not being more clear, but I do know that the fuel sensor is the problem after having auto zone use their device on it.
Oh, well in that case you'd better fix it (or stop driving the car), since it seems like you don't have any other choice if the "test the emissions with less than 8 gal in the tank" gambit fails.
Just to double check, did the Autozone guy tell you the code and then you looked it up and determined it to be the fuel sender, or did the Autozone guy just 'interpret' the code himself? Sometimes codes have multiple possible causes, and maybe whoever interpreted the code got it wrong.
By the way, why do you think it's so expensive to fix? As I understand it, on my truck the fuel sensor replacement involves removing the bed to get to the fuel tank, which is enough of a pain that I haven't bothered, but it isn't actually too hard to DIY. On (at least some) cars, it should be easier because the top of the fuel tank can often be accessed by removing the rear seat cushion.
Could you post the year/make/model of your car and the ODBII code you're getting?