I will do something similar in my Honda Accord, and I need to put the buttons on another site, but when I opened the unit and saw that everything is connected with plastic tape, stop the project.
I was also disapointed when I found that the board with buttons is connected with a proprietary cable. I was expecting one of the standard flat cables. That means you have to keep it connected and keep it close to the original location. In my case I mounted it on the side wall and soldered wires directly to the buttons. I had to create a new circuit board with the new buttons that is mounted below the screen,
As for the central directional control, it is easier. I have got a 250mm ZIF ribbon cable from e-bay. It is wider than needed, but can be cut to the exact width.
The battery connection also needed some custom mounting or can be soldered directly to the battery. I've used some contacts from the old phone to create a new mounting.
The cradle connection is soldered directly to the contacts with a flat cable.
I don't have more pictures to show, but I can send you the one I posted with full resolution that you can see more details.