When the 921s come out of QA hold I would like to hook it up to my Dish 500. Right now I have DISH 500 with two lines coming out of it. One line goes to my 501 and the other to my 4900. I need two more lines for the 921. Would type of switch do I need to get for my DISH 500 to work with all 3 receivers? Do I need a DISH PRO adapter for my 4900 when I get new switch? Is installing the switch easy enough for a do it yourselfer? Thanks for any help.