1) couple of drops of light oil in the freewheel and some spinning might loosen up the old grease and get it working. Otherwise, a new shimano freewheel is all of about $20.
2) New tires / tubes probably wouldn't be a bad idea. Regardless of the lack of wear, I'd be concerned about 20+ year old tires, especially as they've been sitting completely flat for so long. Small cracks in the rubber will likely give sooner than later if not already.
3) Inspect and if needed replace the cables and housings for derailleurs and brakes. Probably some deteriation of these even in the nice cool basement.
4) Mother's Mag Polish on aluminum bits. Turtle Wax brand chrome polish on the chrome are my choices for cleaning up unpainted areas. Hubs, stem, etc should sparkle like new with little effort. I'd stay away from the rims with most cleaning polishes as most contain some wax products that can reduce braking performance.
5) Repacking the bearings (hubs / BB / Headset) is a good idea to ensure that you get maximum life out of them. Bearings should be in prime shape still, but new grease is in order ideally. Marine grease from the automotive section will do, but better quality polymer greases are out there if you want to spend the money (Phil Wood waterproof grease comes to mind)
6) And most importantly, enjoy the process of restoring the mechanical bits and the fact that you'll have a touring bike on par or better with anything out there for considerable more money. There's just something soothing about carefully going over each part of a bicycle. It's such a simple machine, yet one can spend hours polishing, cleaning and restoring each part if they desire.
7) Ride, Ride, Ride!
P.S. - tan sidewalls: they are fewer and farther between these days. Conti still makes a model or two in a tan or skin wall. I have a pair of IRC Road Winner II Duro's that have a tan sidewall that aren't a bad tire either.