Not trying to get all technical, but I gather this is more of a pulled pork in a tortilla than a Carnita. I researched for a while how to make Carnitas and almost every recipe I see for it has the meat cooking in liquid. I never saw a recipe for it smoked or grilled.
That aside, it sounds like it will be great. Make sure and take some pictures...
Terry - KCBS member
LSG 24"x30"x36" Vertical Upright Smoker with Warming Oven
Weber Smokey Mountain 22.5" - Weber Genesis S-330
Pitmaster IQ-120 - Thermapen - Maverick ET-733
For info on any mods I have done to my WSM, please see this post