Yes DIY and actually pretty easy. I did cement backer board around the fireplace and used a refractory cement which is heat resistant. Straight onto the drywall above with a standar thin-set mortar. I beveled the edges on the right side where the wall angles away so I didn't end up with a gap. We have bullnosed wall corners so I built a frame out of 1x2 for the niche to create a straight edge to apply it to. Only $8/ sq ft and no need to grout.
Great business model.
http://www.recycledgranite.com
They get granite scraps from builders and turn them into split stones. Keeps granite out of landfills, builders don't have to pay to dump it, franchisees make money and consumers can get (IMO) a pretty cool product as a reasonable price.