You will need more than a "duct" to the outside, you will need a chimney. And if you live in a cold climate, you will need a chimney that will warm up fast, so a double wall system may be needed.

But carefully look into Vermont Castings. They USED to be among the absolute best stoves out there. But the company has been sold so many times lately, the quality has gone into the toilet. Even stove shops here in Vermont aren't selling them until they can be sure they won't have to go out on a regular basis for service.

As christopherh also wrote, you're going to need to connect to a Class A chimney, either masonry or triple wall (usually) stainless steel. If one of these does not already exist, the installation cost for one would be many times the stove price - triple wall runs about $30 per foot, I believe. You will also have to meet the relevant local/state code standards for a hearth and clearance from all combustable surfaces.