There is a mounting kit that you can purchase to integrate "some" of the DirecTV LNBs onto the HughesNet system. However, I'd recommend separate systems. Getting the dish aligned for Internet and all the TV satellite signals is pretty tough and you'll likely end up with a compromise where neither service is as good as it could be.
Before anyone purchases a satellite Internet system, I strongly encourage you to search your area for wireless ISPs (WISPs). The cell phone companies may also offer service to your area, so check them out too.
If you find that satellite is your
only option, then look at both WildBlue and HughesNet to see which offers the better service & price for your location. There are also resellers (aka VARs) that may offer something you like. I had DirecWay/HughesNet for two years through
Agristar. The nice thing about VARs is that they usually have english-speaking Americans on their support teams whereas Hughes generally uses people in India to handle calls.