I am not sure as to the type of roof you have, but if you take out the cranking mechanism of the antenna, you may be able to see how they ran the antenna cable to the media center. I needed to pull some electrical wires thorough the ceiling and I purchased an inexpensive inspection camera from Harbor Freight (noticed the price is up $20, but if you look online there was a 20% discount coupon that popped up. It really helps a lot. I have used it on so many things in the TT. A worthwhile purchase.
If you can get to the media end of the antenna cable and if you can get to the antenna cable in the ceiling and you tug the cable and it moves at either end you may be able to use it as a fish to pull in the another antenna cable.
If you get a chance we have a WiFi Signal Extenders
Social Group here on the forum. If you have time could you post a little info regarding your project and its performance under the JEFA Tech post.
2013 Jayco Eagle 284BHS
250Watt Grape Solar Panel, MorningStar MPPT 60 Charge Controller
1500 Watt Ramsond PSI, 2 Trojan T145 Batteries (260Ah)
2 - AirSight Wireless IP Cameras (used as rear view cameras)
EnGenius WI-FI extender, D-Link wireless (n) modem
MagicJack Internet Phone
2012 Ford F150XLT, EcoBoost w/3.73
157" Wheel base, HD Towing Package
Our Solar Album http://www.jaycoowners.com/album.php?albumid=329