Other Fuel System Hoses Lines/piping, And Fittings problems of the 2007 Jeep Wrangler

For the past 5 months I've had my check engine light on. I read the code and is says "large e vap leak " I've replaced the pcv valve and the e vap charcoal canister and the check engine light is still on. I've brought it to a mechanic and they did a smoke test and everything tested out good. Showing that there were no problems and to start with the gas cap. I've spent over 100. Dollars on gas caps and I still have the problem. I have to for emissions by the end of December. I've had every recall known to man on this Jeep. I've done research and found out that it could be the gas filler neck itself. How to I go about getting a new one and will it cost me anything? I also have problems when I try and fill the tank. The gas comes flying back out if I try and fill it. Its getting out of hand and the dealership won't give me an answer. I was going to go to. Another dealership but I want to know if this will cost me? I have until December 31 to get this problem fixed or my plates will be suspended and I won't be able to get my plate sticker. What should I do?? the check engine light comes on while stationary and while driving. This started in the middle of may.