The only person who could even begin to tell you that would be either a fireplace contractor, a mason, or an architect.

If it was built originally as a fireplace, that's one thing. You'd have the structure you needed.

If not, if it was built as a chimney specifically for use with a stove, you'd have to build a firebox, a proper hearth, etc., and that could get VERY expensive.

In this day and age your best bet isn't to get rid of the stove in favor of a fireplace. If you want the ambiance of a fireplace, get a stove with a large viewing area, one that can have the doors open (with a screen across the opening) that will serve not only as a fireplace for ambiance, but also an efficient heating stove when you don't want the fireplace function.

I agree with the other poster, a woodburning open fireplace is on average 30% efficiant, most new woodstoves are 80% effeciant. And like he said, get a stove with a big glass door that can be opened wide to get that "fireplace" feel. These days everybody is converting to stoves... its the way to go (or stay in your case). Check out my website for more info in this. www.southernchimneysweep.com

Here is a link that might be useful: Southern Chimney Sweep