Tom, here are a few thoughts:
For power, you can tap into the 12V light
above your dinette, ONLY if you can be certain not to overload that particular circuit.
A long, stiff wire can be pushed and cajoled UNDER the rat fur and reflectix insulation along the shell from your vent location to your power source. Hook on to your new power supply wires (18ga lamp wire works great for this app) and pull through.
As an alternative, you could cut a straight line through the rat fur and reflectix insulation, push your power supply wires under the materials and re-glue the materials to the shell. If you don't like the "scar" you could cover that seam the same way Scamp