Fuel Filler Neck Grommet Replacement
If you remove the screws that hold the rubber piece that attaches to the trunk floor and surrounds the fill pipe, when the gas tank is removed you can dis-assemble or re-assemble everything quite easily. The tube should slide right out, or in, when the tank is moved in a direction roughly parallel to the pipe. Lube up the I.D. of that new grommet with some kind of slippery grease and it'll go back together a lot easier.