I would keep your current DVR and take it in the RV. Why lose that benefit just because you are in an RV. I have a Genie plus an H25 in my RV and it works great. Even though you will only receive the SD version of the DTV programming, everything else will work just as it does now. You don't need to change anything about your account but if you are going to use less receivers than you are currently using you will need to drop them from your account. DTV will send a box for you to return them to avoid the fee if you do not.
Otherwise, just move them and go. You may also find that you wish you had service like you have at home since you will now simply be at home in an RV. The hardware you now have would still work when you find the dome simply does not preform as well as an open faced antenna does and you can get back your home performance plus HD with the "right" roof mounted antenna.