Working with MaxScript to create the plug-in is actually pretty simple. This site was a pretty nice starting point for figuring out where to start with creating the plug-in, and the MaxScript documentation itself is not half bad. I'll likely write up a tutorial on how I went about creating the plug-in at some point in the future, as some parts of it are not so obvious as others. With this, I no longer have to manually code little debug primitives to test things, so I'm quite excited about moving forward to getting the actual game started.
And yes, to answer the question, that is the Yuna model from FFX-2, and Rikku from FFX. They just happened to drop in to help me test my plug-in and make sure things integrate smoothly into my engine. The models came from a place that no longer exists (I believe), so I can't really offer a link to where you might find them, but I'm sure they're still available in some forgotten corner of the internet. . .