Even if you go with Dish and are able to get HD stations, the dome system you have can only aim at one satellite at a time which makes it of little use with a DVR if you want to record one channel while watching another since that could only be done if both channels are broadcast from the same satellite.
I continue to be amazed by major RV manufacturers continuing to install systems such as what you have without giving customers the option to purchase something better. They want to be able to advertise the "bling" of "satellite TV included" by providing the least expensive possible implementation. I wonder what percentage of buyers end up like the OP disappointed by the satellite system they have been provided?