If you want HD Directv and automatic pointing you will need the Traveler dish mounted on the roof, about $2K installed. We have been pointing a sat dish for over a decade and just purchased the same dish (serves 4 TVs) we have at home from Ebay when we went HD a few years back.
Works for us as we often camp among trees and other obstacles, we carry 150' of coax that allows us to position our HD dish where we can obtain a signal. It takes about 5 minutes to point with clear access to southern sky, a bit longer if scouting a shot between the trees.
We love having all the same channels we have at home while on the road, also get locals if we are still in NM. We even set-up HD sat dish when park cable is available or OTA signal is adequate as nothing compares to the full blown package we subscribe to. We don't watch a lot of TV while RVing, but if there is a sporting event I want to watch or a particular program my DW needs to view it's great having the capability to do so.