I'm not here to beat on you; I'm just trying to put things into a little perspective.
As you can see from TomR's post, there are some questions, and those questions can lead to other questions. Jack is for real and I think very real in suggesting that you contact a contractor first. Perhaps, 2 or 3 of them. They'll come to the house FREE of charge and answer all your questions on the spot. Also, the more folks you have come to the house, the more you'll learn.
This Forum is really easy to post one's questions to and later in the night, see what's been answered. If you look at the types of posts 'drawing' responses, you'll see more of what I'm driving at. Very broad questions don't get answers, or they get 'directed' to other sources. If one knew something about the 'nature' of their post, then, perhaps, there would be responses. If you're having trouble selecting a brand HVAC unit, you'll get responses I'm sure. If you want to know if a quote you were given is good, then post up the details and someone will probably respond. You see, it's not that easy to respond to a post like yours especially since it's a very broad one. The time it takes to respond to such a post would take away from time one would want to dedicate to other posts. I'll stop there.
As 'blunt' as you may feel Jack's follow-up is, IMHO, it's not out of line. I'll add that after you have a couple or 3 pros out to the house, post up what additional info you want and someone will be GLAD to help!. My best to ya, and hope this helps.