Brake System Rebuild

Its not dual chamber or double chamber its dual line ( although there are 2 chambers). It amounts to 2 seperate brake systems, one for front, and one for rear. It's a safety improvement in that a leak in one wheel doesn't drain them all. So yeah you'll have some lines to change along with the perportion valve.
As for you that slightly used hardware offered above... it would consist of springs and things only. Nothing that will kill you.
Buying used springs and professionally rebuilt wheel cylinders make a lot better sense than buying new return springs and kitting the wheel cylinders yourself.
As for brake shoes... the original asbestos linnings aren't available. You'll have to settle for whatever is available now for that model.