Not to discourage you, but this sounds like a headache. You are basically re-engineering this guitar. I would much rather design the guitar and THEN build it, rather than take a working guitar and make it something that it wasn't designed to be.
It might actually be easier to keep the neck placement the same relative to the body and change the position of the bridge to match your new scale length. Not sure if that's possible with your bridge, but it would be a lot easier to calculate the new position for the bridge than a new position for the neck.
That said, get the right info, stick with this project, and enjoy the result.