Can't Use King Quest Satellite Dish with OEM Wiring

No A/B switch needed.

Put a 2 port coax plate next to the amplifier plate. Move the outside coax to one of the coax connectors on the new plate. Run a short coax from the other new plate connector back to the original amplifier plate. use a short coax to jump from one of the coax pair to the other.

With the jumper in place, you have exactly the setup you have now. Remove the jumper and you have a home run line outside for your satellite antenna, then connect the receiver output to the tv through the other coax.

If you have a good run from the outside cable connection to the Winegard power supply just follow my directions for adding an A/B switch. Done!
Be sure to use a good A/B switch with a description that includes High Isolation.

Thanks for all the replies and suggestions. Here's where I stand:

-Verified all the cables are RG6 and all ends are good compression fittings.

- Tried bypassing the antenna amp and got power to my outside dish and a good satellite signal back but bypassing the amp costs me the option of OTA or cable signal to the remote TV.

- Tried using diplexers (not splitters) with power bypass but power didn't get to the outside dish. I wonder if special diplexers with one-way power bypass would work.

- Considering a dedicated cable for the satellite but this is a last resort because cable routing is a nightmare.

Best method. Restore all original wiring and install either RG-6 or RG-11 from Receiver to handy dandy external connection spot (IE in a storage bay) This is always what I recommend.

Option 2
Remove park cable lead from back of wall plate (Center lead) and extend to Sat Receiver Do not use diplexers or any fancy stuff just a double female connector (Barrel they are also called) if the Sat Receiver has RF out to tv extend that back to the cable port else leave it un-populated (not connected)

But I really recommend a dedicated sat antenna lead (RG-6 or RG-11) not the El-Cheapo RG-59 they put in at the factory.

Just put it through a window ;-)

You can not pass through a Winegard booster plate but that's easy to bypass with a splitter. You can not pass through the cheap splitters used by most if not all RV manufacturers. You need to swap any splitters in the run out for "power pass" splitters.

In many, many cases there are splitters in the 5th wheel wiring and when that's the case you can't use the cable connection (designed for cable, not satellite) for any type of satellite connection. If you are lucky and there are no splitters all you need is an A/B switch.
Remove the Winegard wall plate and there will be 3 connections. Cable, antenna and Out to TV. Remove the Cable connection and connect that to the single input on the A/B switch. Then run new coax jumper cables from the A/B output side. One will go directly to the satellite receiver and the other will go back to the cable connection on the wall plate.