Tom & Karen,
The needed items you must have are a Dish for the Satellite Service you have... some way of supporting the Dish with a post and a Tri-Pod ... A Length of Coaxial Wire to run from the dish to the Satellite connection in the docking station... a Signal Finding Meter to assist you when you are outside aiming the Dish...
I may be wrong... but I do not think you can use a "Direct TV Dish" to get service for your "DishNetwork System"... I believe they are different types of dishes.. as well as Different LNB's.
OR
Go to your dealer or local RV Center who sells automatic Dish Systems that go on Roof of your RV... Let them install the system and teach you how to operate it.
OR
Purchase a portable but Automatic Satellite System such as VuQube Satellite Antenna. Which you can attach to the Docking Station by a coaxial cable and it will acquire the Satellite signal with a few clicks of a Remote.
Link:
http://www.pplmotorhomes.com/parts/tv-antennas/vuqube.htm
Good Luck with your project. There are lots of posts on this Forum about Satellite TV... just use the Search button...