Sure I'd love to be thin and have hair again, but not if the price was having to relive all the bullshit I went through in my life again. Now, if I could go back and do it all over again but retain knowledge of the future, that would be completely different. I'd do the Biff thing and bet on all the games, then buy stock in Microsoft and Starbucks with the winnings.
And I'd make sure a couple of bitches who really nuked my life died in horrible "accidents," and nobody could ever be able to establish motive.
As for the older part, I used to wish that I had been born 10 years earlier, so I would have come of age in the 70s instead of the 80s. But it's not something I feel strongly about.