Hole in tank fix?

Well the hole it on the top of the tank and since it wont be in the car for a while I think I will see about getting a radiator shop to fix it before ordering a new one. Napa said 250 for a new tank tho.
Since we are on tank topics, can someone tell where the line coming out at the top of the tank goes? is it an overflow line? I also put a pic of the gas cap up and it has a vent in it so can I just plug that line coming out of the tank off?