Congratulations on your new find and welcome to the werkz.
...to start first... *hmm.
In all cars I purchase, I always start by developing a history of my own for the new car; and that starts from replacing all fluids and filters; and then move on to fix, repair , and/or replace what is obviously wrong. ;-)
When i am satisfied with that... i'll move on to mods.
My way may or may not apply to you, but however, you proceed - Good Luck to you and have lotsa' fun with your car.