I would blow out the lines, then run mineral spirits or some other solvent through them to flush out the crud. then inspect the lines to see how they look. it might be easier to simply replace all the lines, expecially if they look really rusty under the car.

as for the tank...is this a budget deal or a "do it right" deal? on the cheap, drop the tank, pour in the same minieral spirits/solvent and swish it around for awhile. then try an engine degreaser foam that you let soak, then rinse away with water. let the water dry and re-install the tank.

or, take it somewhere and have them boil out the inside of the tank, then have it sealed up from the inside so that it won't leak.

unless the tank ALSO looks very rusty, in which case...buy a new tank.