How do I remove natural stone from a concrete block fireplace?

Chimney above roof has cracks in the mortar between the stone and is allowing water to leak into the house. There is way to much linear footage of cracks to attempt to seal. I did spray liquid poly with a garden sprayer in an attempt to fill the cracks, did not seal. I would just like to remove the stone then use some other type of mortar/vinly siding to cover the exposed block.