What type contractor can build a new chimney that has been capped and a new roof laid over it ?

I am thinking of buying a house. It has a beautiful see through fireplace that hasn't been used in decades. In fact, the chimney has been capped and a new roof laid over it. I need to find out, how much it would cost to cut a hole in the roof and rebuild the chimney. I think it is wood burning but am thinking of making it a gas fireplace as well. I just don't know who to call to get this type estimate. Thanks.