I have done gas tanks on old Fords, a Dodge Dart and MY72BUG. Here in the land of nine months of winter and 3 months of unsafe skating gas tanks are a given - ya do 'em all sooner or later unless you learn to oil-spray the living daylights out of them. With the beetle the job was a walk in the park. ( I can't say as much for the others where you have to crawl underneath them and battle the rust demons.) Get the car out into a fresh air environment. Remove anything which covers the tank - any mat or trunk covers. Get a suitable container for catching the gas. Make sure that you have left as little as possible in the tank. Mark and then undo any wires, pipes hoses etc. Around the rim of the tank you will see bolts with big washers - four of them. Undo the bolts and lift the tank up out of the luggage compartment. When the outlet line is exposed, remove it and catch the remaining gas. No smokes or trouble lights or any source of ignition is allowed while you are doing this. Clean up the underside of the tank and look for anywhere which has been seeping gas. Outlet lines are a likely source of leaks. If you can't find the leak, put a couple of cups of gas into the tank and tilt it around. The leak will expose itself. If the whole tank is rotten, replacements are available. If your problem is the outlet line, pick up some new line rated for fuel transfer. A handy thing to get is a product called "Seal-All". It reacts to gas and makes a permanent hard gel-like seal even without removing the fuel from a tank. Use it also as a bonding agent when you are putting hoses back onto the tank. It will deal with the gas smell that can be ever present with the luggage compartments of Beetles. When you are returning the tank into the car, make sure that you don't crimp the outlet line or you won't have any gas going to the carb. Use only nice new clamps for the job. If you are reusing the tank and it hasn't seen a proper cleaning since the factory, take it to place that services fuel tanks and they can do a number on it. Money spent here is a savings in the long run. Blasting all of the crud out of the fuel system is time and money well spent. If the source of the leak is the fuel line from the tank to the carb, consider replacing it with a line on the underside ( not inside ) the utility tunnel. This is way easier and is another way to eliminate fuel smells from inside the car. Good luck with the project. Dan (MY72BUG) in Goderich, Ont.
I'd rather have a partial bottle in front of me than a partial frontal lobotomy.