A lot will depend on what you want and your mechanical skills. If you want the bike to last, plan on doing a basic cleaning and lubing of everything (bearings).
If the tires are 40 years old, I'd also go with a new set of tires, perhaps upgrade to something more durable than was originally on the bike.
Hard to say what to look for. Wheel rust? Spoke rust?
Broken or missing parts?
It will be a fun project if you don't get too far out of your element. As mentioned, it will be hard to justify bike shop rates to fix it up.