I have to admit that most of what I would do is extremely shallow.
I'd go back to 1977-1988 and do my best to have very raunchy sex with Harrison Ford when he was at his most magnificent. And then I'd mainly go see all the bands I never got to see - Ike and Tina Turner with the Ikettes, Queen (on every tour), the Beatles, the Rolling Stones when they were young, Elvis, Sam Cooke, all the Stax-Volt people, Aretha etc.