Ron, You do infact have 120 volt ac line over the dash and you could tap into this and run id down the corner post and under the dash. You will want to check to be sure that you can have it live with the key on if you need it while underway. The corner molding at the ceiling and wall is a cover for a wiring chase as well. Good luck and if you need more help feel free to ask.
Mike, Amy & Muffin, Full Timers
RVSA Certified Master Technician
iRV2.com -Gulf Stream Owners Forum Leader
2000 Scenic Cruiser
99 Chevy Silverado 4 X 4 Toad
2006 Saturn Vue AWD Toad
NASCAR #3 & #8