I would keep the two you have now.. They will work with the carryout, Some of the more modern receivers will not.. Make sure you transfer service to an "RV" account so you can subscribe to Distant Network Service.
Also make sure the antenna you get is a "DUAL" (means it has two outputs and can run 2 or more (With switch) recievers, a SINGLE can not do this.
(Two LNG's (DISH-5000) is called a TWIN by the way).
If you want HD.. then you get new receivers and the proper open face antenna (SWM) and ... Well, that's about all there is to it.