Hey zigster,
You're best off finding the wire for the high beam at the back of the lights, would be the easiest and most accessible place, you will need a longer wire to the console switch though.
Rubber grommets - pick one you can access from both sides, push a hole in it the push the wires you need through individually or in their condute you're going to use. The condute method may be a little harder to do.
You will have to negatively switch the relays (below), this is how my L is wired and i'm sure it will work with your liberty too. Sorry that it looks like a 5 year old's drawing, i'm not fantastic with a mouse and couldn't find basic shapes in photoshop... Hope its of some value.
Cheers
Bennie