93 ford ranger gas leak

My little ford ranger has a gas leak. I can't fill
it up more than half way. My mechanic says
it's the fuel neck and when I  driving it
splashes around and that's what's making it
leak. But when I'm filling it n it's jus sitting
still it will leak until the tank is half way. I
think it's more than just a fuel neck piece. I
don't wanna buy that then have to come
back n ha e him year it apart again if he's
already finna have it open to actually fix the
problem what else should I be getting fixed