[pushkins]

Chimney rebuilding is not for first timers, no matter how good your masonry skills are. The flue will either have to be clay or if your going to install a whole new flue system then it will need to be sleeved with S/S all the way down to the fire box.
One thing to remember is that the top of the chimney must be 2' taller than anything within 10' of the chimney.
Very often when they knock down chimney's they damage the existing flue, this must be checked and if cracked replace any and all damaged flue tiles.