The thing about installation is that if it isn't functional, it isn't really installed, now is it?
The dealership doesn't want to be held responsible for troubleshooting the brake controller install if it doesn't work after they mount it and you modify the connector.
Since your vehicle only has a flat connector it is highly unlikely there is a brake controller connector under the dash.
You should convert your flat connector to an RV connector and ensure it works. Then you, your buddy, or the dealer can wire in the universal brake controller under the dash. Connecting it to the vehicle's brake pedal and running the trailer brake wire back to the RV connector.
This is the most logical way to go about it, and the one most likely to succeed.
Also, you can rest assured the dealer is charging you a Prodigy P3 price for a bottom of the line controller.
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