I'm sure there will be a pic somewhere of how they go together
As for adjustment the double nuts are to "lock" the callipers together, just tight enough so that they move and spring apart.
As for one pad hitting first, try the single nut that holds the brakes to the frame, undo and then bodily move the calliper a bit as tightening the nut can twist the calliper round, failing that with the brakes on the frame pick the spring that is on the side of the pad against the rim, pick it off with some fine nosed pliars and pull it towards you and then tuck it back onto the calliper, this will unilaterally tighten the spring and even out the pads.
Finally before you do that ensure the spring top is horizontal as tightening the holding bolt can twist the calliper (as mentioned). It's acceped that you can take a "drift" and smack the spring just as it exits the centre of the brake to level it off...allegedly.
Anything on Sheldon Brown.
PS I run Weinmann 500's on my Jackson, they were light, and dirt cheap and Weinmann did all the spares. There must be millions of them kicking around if you have lost something