From your post, it seems you already have a 'dome' antenna on the roof? If you do then here is my response:
Is the in motion satellite something we need to get through our cable/internet provider at home?
YOu would call a Satellite provider to get service. Either Dish Network or Direct TV.
What is Winegard?
Winegard is a manufacturer company name. They make things like Television and Satellite Antennas.
Do you buy a dish/dome from them and then still have to use a provider like Dish or Direct TV?
Your post sounds like you already have a 'dome' on the roof since you say something like "talked us out of activating the in motion satellite". Do you?
And last, will Apple TV work in place of an in motion satellite?
this is probably more complicated than activating and operating satellite. This probably needs it's own thread.