I had done this with my old PSP way back in the day, however it's been a while since I've messed with any of this, partly cause my Vita was always pretty up to date. I was just able to get it back down to 3.60...
So, I guess my main question is, what should I do? What all can I do with it? I've just been googling for most of what I wanted to try, been able to make it all work sofar, but not sure what all I can do.
There's all sorts of homebrew games, emulators, and ports for the Vita, as well as the ability to launch the PSP firmware and run PSP homebrew. You can also run plugins to mod existing games. One of the best things is the the Vita HomeBrew Browser, which is like the App Store where you can see a big list of homebrew projects to download directly to the system.