Binny,
I PM'd you with a link to photos of a remodeling project where I had French doors installed to close off a game room.
It was really hard to find photos and ideas to guide me when I was trying to decide what to do here.
First, I think you need to decide what kind of door you envision: a solid wall with a regular, solid door? Multiple doors? French doors with glass panels?
If you can make a sketch of your idea, even a very rough one, it will be easier to get your expectations across to anyone who's helping you with this project.
I don't think the height of your ceiling is a showstopper. A good contractor can fill any extra height with a sheetrocked wall, or high windows. My French doors were custom-made to fit my space, and the price wasn't much more than than the ready-made ones that Home Depot carries.
Are you planning to do this yourself? We didn't even consider it, but you may have more experience with this sort of thing. Just to give you a rough idea of budget, I think this whole project (the doors, installation, and painting) ran under $1000.