Question Presently bone-stock, want to get to KitKat, where do I start?

I have an original TF201 from the first 6 months of production. I haven't used it in a few years, out of frustration with the lack of updates. It is untouched, unrooted, bare OS of the latest release. Now that my warranty is expired, I think I'd like to:
  1. Unlock it
  2. use nvflash to back up the encryption
  3. replace the bootloader
  4. replace the OS with Kitkat

Is this possible? Am I on the right track? What do I need to do to start? I don't want to brick this thing.

Tangent, is it worthwhile to do this to a TF201? Will there be significant improvements to performance and functionality? Stock it is a bit sluggish and no longer able to use much of the play-store or many google apps. It's useless to me in the current state.