Welcome aboard!
I'd start with a good, thorough cleaning - It sounds silly, but this is a good way to familiarize yourself with the car and it'll also point out any new leaks or problems with parts.
First step: Pull the plugs out, and when you do, spray some oil into each spark plug hole... maybe a teaspoon. This will give the oil time to lube up the rings and work its way down the cylinder walls.
Up on jackstands, change every fluid... Coolant, oil, trans (ATF or gear oil), diff oil, brake fluid, clutch fluid... ALL of it. Drain any fuel as well - Siphon tank and blow air from the fuel line at the fuel rail on the engine, get it all out.
New spark plugs, fuel filter, air filter, oil filter, distributor cap and rotor.
Fresh battery - Don't even mess with it if it's been in there 5 years. It's dead.
Check battery cables, make sure they're not corroded. If so, swap 'em. Cheap and easy insurance.
Check belts and hoses for crunchiness. Replace if necessary. Fuel lines are probably getting funky by now, so it's a good time to do those. Do the radiator hoses and coolant hoses on the engine while you're at it, and a thermostat would be smart as well.
Pull the coil wire off the distributor and hit the starter a few blips... just to move the cylinders in their bores.
Fill it up with fresh fuel.
If it sounds normal when you hit the starter, plug in the coil and give it some cranks. It might take a bit for the fuel pump to feed the engine, but she should start. Then, shut it down, wait a bit, and fire it up again. Check for leaks / smoke / explosions.
Another oil change after 100 mi or so would be smart. She'll need tires (they're shot after 5 years, even if they have good tread. Keep an eye on it for issues, but the S-chassis was a pretty bulletproof car - Should be good for a long time.