Go to
www.Winnebago.com. Click on “Owners.” Then click on “Owners Tools” from there you can find parts lists and Operator’s Manuals. On that page is a box titled “ MOTORHOME KNOWLEDGE BASE” click “find information” in that box and it will take you to another page with wiring diagrams, plumbing diagrams, etc.
You can find drawings and such that can provide clues about how things are setup.
On my outside TV there is a fabric strap behind the tv at the bottom. Pulling it releases the tv mount and I can swing it out to get at the connections behind the tv. I’m not sure if that applies to your Vista LX or not.