the first thing you should try doing is locating the leak. 2nd it is cheaper to replaces the fuel line than it is to patch it. for about $12 you can get a 25 ft roll of steel fuel line. you may not even need to replace the whole fuel line. just the section beside the gastank seems to really rot.

 

No need to be sorry about wanting to learn as none of us were born with the knowledge we share. Replacement is the only safe way to go. If a line has a hole you can bet there are more weak spots just waiting to let go. Fuel line is available in rolls or pre-made lengths that have the fittings already installed. If you find the leak you just remove the old line, measure it, go to the part store and buy a new one. If the leak has been caused by rust I would suggest that you replace all of your fuel lines. Some knowledge about proper bending procedures of fuel lines is needed to prevent kinking the line. If a line needs to be cut you must have a flaring tool and know how to use it. Cutting can usually be gotten around by some artful bending of a slightly longer line than is needed. The pre-made lengths are a little more expensive than buying by the roll but usually does not require cuts and flaring.

If you want to work on your truck, the best advise I can give is get a good manual first.