Restore 81 Buick to driveable condition

1981 Buick has a completely restored exterior. I would like to drive it again, has been parked outside for 5 years.
What parts should I replace, such as seals, hoses, brakes, tires (which were brand new 5 yrs ago) -
that may have worn due to non-use and the elements?

The trick is to make a car go and stop so let’s start there:

Don’t be tempted to turn if over using the starter right away. Instead, take the plugs out and turn it over by hand to see if anything is binding or seized, just by way a precaution. It could be perfectly fine but you never know and you don’t want to fry a starter to find out.
Then don’t start it yet. Get rid of what’s in the gas tank and disconnect the input line to the fuel injectors (or does that thing have a carb?). Put a small container under that now loose hose and try to start it. See what comes out. Replace the fuel and air filter.
Then add some gas to the tank, put the plugs back in and try again, this time live.
It may need some nursing to start up with some starter fluid in the intake.

Bleed the brakes definitely and probably replace at least the pads.
Those tires may be suspect - Inspect them for dry rot if they’ve been sitting.

Other guys here no doubt have many more good suggestions.

Be aware that 1981 was the absolute worst year for the automotive industry. This is the first year cars had computer controls and closed-loop emissions systems. You can expect nothing but problems…And yes, it has a feedback carburetor which will need to be rebuilt and few mechanics today have that skill.

So with nothing to lose, try this…Pump up the tires to the correct pressure. Check all the fluids. Add 5 gallons of fresh gasoline to the tank. Install a new battery. Remove the lid from the air-cleaner, open the choke with your finger and spray a nice big blast of WD-40 down the throat of the carburetor. Crank it. If it starts, hey, good for you! If not, spray a little starting fluid down the carb throat and try again. SOMETHING should happen this time. When you reach this point, report back here for further instructions…

I did put a new battery in, in spring and it started no problem (I had to move it for street cleaning). The gas is old, it does have a carburetor, the other things mentioned by you both - THANK YOU. The car has 100,000 km (not miles…km) - it was my mother’s car and then my aunt drove it for a while. Both of them drove very little, and the motor was rebuilt with only 5,000 km on the rebuild. That is why I kept it, and now my son wants to drive it.

That puts a different light on it…There is no reason you just can’t clean it up, check all the fluids and put it back into service…But it IS 31 years old…Have it checked carefully for corrosion damage. Have all the brake lines inspected and replaced if there is any question about them…There are at least 5 rubber brake flex-lines. 31 years is long enough…Your life depends on the brakes functioning properly…Check the steel lines inch by inch for corrosion damage…

Since you count distance in KM, you must be in Canada, the land where rust roams the planes.
Have them look at the shock towers and related suspension stuff as well. It may be fine but better safe than sorry. Since you’ll have your brakes inspected, it is a no brainer to do that as well.

Edit: I just noticed your name. “Calgary” is not your last name but where you live, I take it.
If so, definitely check for rot and rust if something has been sitting that long. I trust it was garaged?

RemcoW, no it was not, I am embarrassed to say. However, it was stripped down to the metal, rust cut out and replacement metal welded (no filler); a superb paint job, no question. The rear bumper was not salvageable (ALL the rust from the prairies did indeed settle there), but after several months, I did finally find a replacement. Brakes is one place I do not want to save money or effort, as I believe the same.
Good information, again thanks for taking the time. I didn’t know this site existed, looking forward to checking back frequently!

After sitting this long I’d drain all the fluids (engine oil, transmission, coolant, brake, power steering), replace them and associated filters, replace fan/serpentine belts and timing belt if equipped with a timing belt. Replace the thermostat, radiator hoses and heater hoses.