Watched this with interest the last couple of weeks as we still have the MV3500T on our rig. Didn't respond because we are DTV subscribers.
I would call Dish directly. If they are anything like DTV (now AT&T), that will be a lesson in futility. Also try 3rd party folks that sell Winegard. We have had great luck with SolidSignal. They are happy to tell you, sell you or not.
The problem with the MV3500T is that, it has been discontinued for a number of years now. No parts support I can find. Also, it only receives SD. Winegard used to offer a HD interface, WB-2000, replaced by the WB-2700. Both now discontinued.
The upside of the MV3500T is that seems to have been well made. Ours is twelve years old, and just keeps on keeping on. Full disclosure: the gears are nylon or something and ours have worn a little, such that it searches a little to lock on. In an earlier post I described how I replaced a worn train gear with a gear I had taken from a Magic Chef microwave oven.
IVO the cost of a new comparable SD ($500+/-) dish or a new HD ($1800+/-) dish, we are well satisfied using the MV3500T for overnite stops, and running our HD tripod out from under the trees for longer stays.
Don't know if you have these, but here they are.
MOVIN' VIEW MV3500_REV 1-10.pdf
MOVIN' VIEW MV3500T_Rev 7-07.pdf
Fair Winds and Following Seas