1998 Ford Mustang fuel tank gasket

There is gasket where the gas fill tube enters the gas tank. Took everything apart but could not get tube out of tank to replace gasket. Wasn't enough room to get it all the way out with the constraints of the frame and the body. Has any one replaced one of these before? Do you have to remove the gas tank? Seems like a lot of work for such a simple repair. Any advice would be appreciated, thanks.