I want to start with two minor changes:
First, I go back to 1970, keep Jimi Hendrix from ODing (maybe see if I can get him to kick the smack, too), and enjoy the music of Hendrix Emerson Lake & Palmer.
Then I jump back to 1985, and use the difference in popularity over time of the first three Star Wars films (the most popular, The Empire Strikes Back, was written by sf author Leigh Brackett) to convince George Lucas that while he is an awesome director and producer, he has the scripting abilities of a brain-damaged minnow. I convince him to hire Timothy Zahn to help script the prequel trilogy, which will then be amazingly mindblasting, rather than being the saga of a whiny little emo boy who grew up to be whiny little emo Darth Vader ("NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO!!")
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Sodium is a metal that reacts explosively when exposed to water. Chlorine is a gas that'll kill you dead in moments. Together they make my fries taste good.