As far as repairing the tank, you might want to look in the local Yellow Pages under either welding shops or radiator repair places. They might be able to repair the tank where it has rusted and worn through. If you cannot find anybody to repair the tank, then I would start looking to a junkyard for a replacement. You might want to try www.car-part.com for a gas tank. I think that all years of the T100 had the same size tank, just the '93 & '94 had the tank filler on the opposite side. I can't be sure that the '93-'94 model tanks would fit your '96, but anything from a '95-'98 model T100 would.
As far as the lines, kewlynx said it best. "GET NEW LINES".