For the ghost-shifting, try tightening the down the little screws that hold on the shift levers. They are intended to be adjustable to however much tension you need. And yes, get new brake pads, Kool-Stop and others make suitable replacement pads for your brakes, made from modern compounds which will improve your braking immensely.

Here's a picture of the Stronglight (49D?) crank on my brother-in-law's 1979 PKN10, your bike should probably have one of these if you want to take it back to original, but it's no big deal.