Oh so many different configurations to consider. If you have the older (2005/6) tv you most likely have the RCA audio output jacks on the back and as stated they would go into your audio input on the DVD. Just remember that you are outputting left and right stereo and to have true surround sound the amplifier needs to convert it to 5 or seven channel. Most RV's do not have that capability so what you will end up with is a similarity to surround sound, in my opinion. But it is still better than the tin type speakers of the TV (my hearing capabilities)
When i replaced my 2008 vintage television, it was the long back, 117 pound variety but it did have a digital tuner. The output was RCA Phono jacks. The new tv I replaced it with did not have RCA Phono jacks but did have HDMI Input. The DVD player did not have HDMI at all. The tv also had DIGITAL Audio fiber output. The DVD player was not capable of fiber input or output. You can see that there are many, many different configurations and the ones I mention only scratch the surface.
I was able to find a digital to analog convert. I plug the fiber optic cable into the convert, and the RCA output plugs of the convert into the DVD player. It suffices to give me some additional audio using the "surround sound" speakers.
Good luck, happy trails, and as a HAM I know you can work it out.
Wayne MSGT USMC (Ret) & Earlene (CinCHouse)
2008 Winnebago Destination 39W
It is what it is, and then it is what you make of it.