I would like to add a thin stone veneer over the lower part of my home's exterior as an accent. The house is well built with correctly installed stucco. The stucco was completely painted with two coats of Dunn Edwards paint about three years ago. What type of surface prep is necessary to add the stone veneer?

I live in AZ where moisture is rarely an issue.

Being that the home's exterior is already stucco, the only prep work you have to do is apply galvanized metal lath to the area of the wall you intend to install the stone veneer. You should use Tapcon masonry screws (blue screws) to attach the lath. To aid the mortar in adhering you might consider applying a bonding agent to the existing stucco surface prior to installing the lath, but this would be precautionary not mandatory. If your current stucco has a screed or weep key near the bottom of the wall, you will want to have your stone veneer at least 1 inch above the key to ensure that moisture is allowed to escape. I know you've stated that moisture isn't really an issue in AZ, but you guys do get rain once in a while, and other readers may benefit from this info as well. Good luck.