TN-V and ARK are PSP-side kernel exploits for the Vita. TN-V is my personal preference because of the fact it boots you into the PSP XMB, so it gives you that feeling as if you have a hacked PSP.
^ TN-V and ARK allow you to play PSP/PS1 games with no fault. (At least not yet for me anyway...)
Rejuvenate, on the other hand, is a native Vita hack that is userland only. There are no native Vita kernel exploits just yet, and you can't play PS Vita backups yet either. But there is some pretty snazzy homebrew in store for it!
Also, you are on the right firmware version to follow to my noob hacking guide to do all those things, if you haven't seen it already!