Is it truly a "dual" LNB, or a "twin" LNB? Early Dish500 systems had two separate LNBs, one on each half of the Y-adapter; an external switch was required. If you have this setup, you'll need to have two available feeds from the switch; if not, you'll have to replace the switch and/or the LNB.
Newer legacy Dish500 systems have a "twin" LNB with two feedhorns and an integrated switch in one housing. If you have that, you will need to run both feeds from the LNB to the 522. If you're using the other feed for another receiver, you'll have to add a switch or upgrade to a "quad" LNB.
You also didn't say if Dish is aware of your move (i.e., they moved the dish, or you changed your address with them). If they are, then you can't get new-subscriber deals, though you may be able to upgrade your receivers under existing-subscriber deals. However, if you have a new address/phone number AND your account is still at your old address/phone number, you MAY be able to sign up as a new subscriber using the new address and phone number.