[folivier]

Look at the ceiling where it joins the sidewalls. At least on the 1990+ models there are curved panels that can be removed where all your wiring is run. Or if you have valences over the windows you can lay the wire in there. These panels should also be accessible in the cabinets.
If you're replacing the camera also you can use the old cable to pull the new cable. Just take your time and use those access panels to help.