It should be ride-able if you re-lubricate the bearings, derailleurs, and cables. Aluminum rims are a plus. If the wheels are true, that's a big plus. Given the relative lack of wear on the rims and brake pads, it might not have gotten much use before being stored in a dusty garage or shed. Whatever grease Schwinn used lasts a long time, but maybe not that long. My preference when approaching a bike like this is to get it working as-is before deciding what needs to be replaced, if anything. The rubber will have hardened just due to the passage of years. The biggest expense will be new tires, but you might as well ride it gently on the existing tires if possible, to see if the bike is worth keeping. Put a drop of penetrating oil in each spoke nipple, in case truing the wheel is ever in the future.
Any part that is totally unworkable to the point where it has to be replaced, aside from the tires and pads, would surprise me.
I've had great luck with the Jagwire Basics brake pads.
Good luck! I ride a couple of Schwinn frames of that vintage, that were nowhere near as nice when I got them.
Last edited by Gresp15C; 08-28-20 at 08:24 PM.