You'll have to visually inspect the linings to see how badly they are
affected. On something this old, there is the chance that the metal brake
line is badly rusted and the nut wont turn on the tubing. Soak it with
penetrating oil and, using a small pair of locking pliers (vise grips)
squeeze the nut on as many opposing faces as possible - this can often free
up the nut. If the line is badly rusted, it should be replaced. Premade
lines are available though yo may need an adapter at the wheel cylinder end.

If it's been leaking for any length of time, you'll likely find that brake
covered in distasteful goo... hardware and all. Given the age of the
vehicle, you may opt for a spring kit rather than trying to clean the old
stuff. If it were mine I'd likely replace the shoes on both sides just so I
wont have to go through the process all over again in the near future.

HTH