Congratulations. A very nice vintage example of Airhead.
I recommend not trying too many "upgrades" right away. The bike will work just fine the way it was built. There's plenty to do. You'll need a manual either the Haynes or Clymers manuals will work. Most of us have both. You'll need the on board tool kit and a couple of special tools will be needed in time. There are many parts that the bike will need as normal wear and tear. There's the oil filter set up to learn and measure the oil filter depth to see if the White O-ring is properly spaced. The tune up on this machine requires points and plugs. You learn how to do this. Clutch adjustment should be looked at and all the fluids changed.
The bike will tell you what it needs. At first you will be learning to do this normal maintenance stuff and then some day there will be a new oil leak that we'll have to talk about. Or the clutch may need renewing or the gearbox might be getting too loose. So learn the bike. It will tell you what it needs.
Most new Airhead owners want better brakes right away. Eventually the brakes can be improved. If you throw thousands of dollars at the brakes and a year rebuilding them, they will still be Ate brakes and they won't work as good as your buddies new GSXR. Learn to not tail gate. It can save you thousands of dollars.
Let us know how well it runs. Put some miles on her.