The stone work is underway, and it's turning out better than I had hoped. It's certainly more art than technical skill. Once I figured out the proper mix for the mortar things started going pretty smoothly.
I'm using 'manufactured stone' which is basically concrete poured into forms and tinted. It's about half the weight and half the cost of real stone, and much easier to work with. No, I didn't get it from Lowe's - there's a local concrete supplier who got me everything I needed.
I found that mixing less than a gallon of mortar at a time was best, because my skill level is low so I'm slow at it and that keeps the mortar from getting dry.