You can use it, but the dish 500 will only pick up 119&110. If you need, or want HD programming with it, you will need a 1000.2 (119/110/129), or 1000.4 (61.5/72.7/77)
If thats the case you'll need a DP21 switch and your 129° dish will need to have a Dish pro lnb too. It's probally easier just to get a 1000.2! Unless you have the second dish already laying around.