I am currently a D* subscriber but don't have any HD recievers. I'm looking to upgrade to HD. I currently have two dishes on the house, had to add 1 for local network feed. If I upgrade to HD equipment will I still need two dishes? Will the ones I have work or do I need new dishes? Are the bigger? smaller? Will the fit on the existing mounts? And lastly is the HD install something I can do on my own?