This may or may not be a blessing...a lot depends on how old the system is that you have, and if DirecTV or DISH will work with the system you have.
You will probably do best working with an RV Service Tech, who specializes in these systems, or as I did, which was to try a Marine Tech, since the systems on boats are virtually the same, and I live near the water, so it was more practical. It was the DirecTV guy who told me to try them, because he couldn't do anything with the system that I had. It was about 6 years old, and may have been fine for the previous owner, but I ended up having to buy a new box that would work with my old in-motion dish....so I was very limited in what I could actually watch....NO HD for ME!!
Eventually, I just waited until the contract with DirecTV expired (almost 2 years), having paid a small fortune for vertually no TV. We decided that we will bring DVD with us, since we really don't plan on watching much TV when we're out anyway.....maybe on rainy days, if we get tired of board games:)
And, we can stream movies or TV on the computer with our aircard, which I also use at work, so it's worth the investment.
You really may have had the same walk around that I had.....flip the switch for the dish, to hear it spinning around, but not seeing anything on TV, since the box wasn't "activated"....trouble is, the box couldn't be activated.....so now it just sits there, and I've got a dome on the roof....probably knocking my fuel mileage down some more!
Good luck!
Oh, if you already have DirecTV or DISH, it may be fairly simple to just get a portable dish to use when you get to campsites....IF, you have problems with the in-motion dish. If you in-motion dish does work, it is really great!! We have one on the boat I work on, and I love it!! I just wouldn't invest in it for the RV, when I can watch DVDs or use the computer.