If your fireplace now draws ok, I would think that the wood stove would be just fine going into the same flue as the chimney. But you probably would have to keep the fireplace damper closed while using the wood stove, and keep the wood stove damper closed when using the fireplace. Once a fire is established in either the stove or fireplace, the draft would probably develop strong enough to burn both (maybe). Having said all that, venting two wood burning "appliances" into one flue probably doesn't meet code. Check with your building inspector? Dodgeman