There are several places. Your base ITT will be able to give you information on the tickets and can sell them to you in advance so you can line up Fastpass+. I like
http://www.militarydisneytips.com/ for all things Disney/military and they have a good page here about the Military Salute discounts:
http://www.militarydisneytips.com/Disney-Armed-Forces-Salute.html. There are a few other sites with good info. I think there even used to be a military forum here on the DISboards but I don't see it anymore

You can book directly through Disney for the rooms (I'm fairly certain you have to call, I can't figure out how to get the mil discount online) and you can either get the tickets through Disney or, like I said, through ITT.
I don't think SoG has discounts (though they have package deals) but they are cheap compared to the other resorts. I was referring to the Military Salute room discounts at the normal Disney resorts.