Gas cap

[Red323is]

My gas cap would not click-closed and is apparently worn, so like it said it would, Check Engine light went on. Bought the proper BMW cap at Autozone (it's Sunday my mechanic is closed). This one doesn't click that well either and light is still on. So it must mean it's the other end that's worn, the part the cap attaches to? What's involved with this repair?

And my Climate Control unit just bit it yesterday :(