Georgia46,
Welcome to the Heartland Owners Forum. You'll find a lot of useful information here along with a great bunch of people who are willing to share their knowledge and experience.
Selecting a dish involves making several preliminary decisions:
1. Service provider - Dish, Directv, other? If you already have satellite at home, you may want the same service in the RV.
2. Standard definition vs High Definition: Your new Bighorn has high definition TV. You can use a standard definition dish, but the picture will not be nearly as good.
3. Manual aiming vs automatic aiming: pushing a button to find the satellite is much easier and faster, but more expensive. And to get automatic aiming with high definition for Directv, the dish will be more expensive.
4. Rooftop mount, carryout, or tripod mount: Rooftop is easiest, is automatic aiming, and requires no storage space, but may not work if you park under trees. Also it's likely to be most expensive. Most carryouts are now automatic aiming and can be positioned to get a clear view of the sky. Tripod mounts are manual aiming, least expensive, but take longest to set up and aim.
Apart from cost of the dish, there is the cost of the receivers. You can purchase outright, or lease. In order to lease, you typically have to sign up for a 2 year commitment for programming, paying each month. If you only use the RV for 1/2 the year, you may be able to suspend the programming charges while the rig is in storage, but only months of active usage count toward the commitment. Early termination is expensive.
I realize this is all pretty daunting, so here's the simpler answer:
Get the Dish TV pay as you go program with their Tailgater Dish and matching receiver.
Here's a link that explains it.