I'm with the Army this one. Buy a good unit. Either the Furrion he mentions or the more expensive observation version are very good at maintaining a signal over 30 feet. I bought the observation unit version with the mounting bracket as my trailer didn't have one pre-installed. If you have a bracket that looks like what Army linked to...then you can buy that unit without the mounting stuff and it should just plug in. If it's preinstalled for another brand, then you need to go with that. If your trailer says preinstalled, but it only means the wires were run...then you can do what you want.
I connected mine to the center observation light...directly below the light by 3 inches and cut the wires from the light and soldered both the camera and the light power to the factory light wires that I found under the light fixture. Easy install. You have a toy hauler, so your installation may be different. But the idea here is get a good wireless unit, tie it into the trailer lights power, turn on your parking lights for camera power and enjoy!
2015 Sierra 1500 Denali
2014 Coleman 249RB
David Jon Devoucoux
People, Places & Things...for over 40 Years!