If you've never played around with satellites before then it will be tough to figure out. Find a use or new portable self setting satellite dish. Wingard. Tailgator, etc. Then you need a receiver for it. The 211K is the norm but there's also a new one called the Wally. It has more features.
It will cost around $35.00 IIRC a month since you don't have Dish already.
With the portables all you do is set it on the ground, table or the roof of the RV. It needs to be pointed towards the satellites to start. Then you follow the tv on screen menu. Once you do it a few times it's really simple.
I prefer Dish because I can get an HD picture with the portables.
If you go the manual setup route with DirecTv you will have to learn how to point the dish. Not impossible but definitely harder. I don't know what DTV will charge for service if you don't have DTV at home. Dish caters to RV'rs so it easy to communicate with them.