I wouldn't advise taking that fireplace down unless you are knowledgeable of the work that needs to be done.
In other words looking at the drawing provided and the heating supplies locations you can clearly see that there is a # of joists resting on the side wall of the fireplace.
This structure would have to be reframed on both levels in order to properly support floor and ceiling joist which would be left free if the side walls where ever removed.
In addition opening on the roof would have to be addressed afterwards.
My suggestion would be to incorporate that fireplace in to the design somehow else.