Vacuum caps won't work, the fuel will eat the rubber if you ever fill the tank above the level of the sending unit. Soldering wasn't all that hard, since its low temperature the solder doesn't really run all the way through, as it moves away from the end and the solder gun it hardens up and plugs the hole (if you keep the heat down). It took me a couple of tries, but worked fine once I figured out you can't just do it all at once. Solder a little at a time, giving the solder the chance to harden and the tube to cool a little and its no problem. As for needing it again, the solder can be melted out pretty easily, which you'll notice if you bring in too much heat with the soldering iron, all the solder runs out and you have to start over...