Usually dish looks at 110* and 119* birds for main service, and Super dish's may look at 3rd bird for locals at 105* or 121*. Dish also uses a bird at the 61.5* location (This is the same bird that VOOM uses) to offer some forien language programs and CBS HiDef channel out of NYC. If you current dish network currently has a dish pointed at the 61.5* bird then that dish can be used for Voom also, but you will need to be careful on what type of LNB that dish is using. If it is using the older legacy style of dishnetwork LNB's you will be fine, But if it uses the newer DishPro style LNB (DP LNB's do frquency stacking, legacy lnb's do not) you will have to change it to a legacy style LNB.
I am currently doing the oposite of what you are looking to do, I use my Voom dish pointed at the 61.5* bird to allow my Dish Network 811 HiDef stb to get the CBS hiDef signal out of NYC. This works well for me becuase i get a digital signal on all my major OTA stations ABC/CBS/NBC/PBS/FOX, but only ABC/FOX/PBS do true hidef currently, so i use the Voom dish to also pull in CBS hiDef for me on Dish Networks tranponder on the 61.5 bird.