Re-designing an existing fireplace
I am willing to tackle most DIY jobs in my house, but I, personally, would draw the line at the hearth/doors/mantel on this one.  

I'm not willing to mess around inside the fire box or chimney of my fire place, nor with the gas lines or any masonry that is not part of the facade.  When I do have to work on stuff like that, I either bite the bullet and hire a licensed/insured professional, or at the very least, enlist help from a friend or family member with true professional experience.