Prepare the wild rice according to package directions.
Meanwhile, heat the oil in a large nonstick skillet over medium heat. Add the onion, celery, garlic, and thyme and cook, stirring frequently, for 6 to 8 minutes, or until the onion is soft. Add the Madeira or broth and increase the heat to high. Cook for 2 minutes, or until the liquid is evaporated. Remove from the heat and stir in the apricots and wild rice. Season with salt and pepper.
With a knife, make a 1" slit from one end of the pork to the other, keeping the sides intact. Push the meat back from the slit to create a "tunnel." From both ends, stuff the cavity with the rice mixture. Mist the pork with cooking spray and season with salt and pepper. Preheat the oven to 350°F. Heat a large ovenproof skillet coated with cooking spray over medium-high heat. Add the pork and cook for 4 minutes, or until browned on all sides. Place the skillet in the oven and cook for 25 minutes, or until a thermometer inserted in the center reaches 155°F and the juices run clear. Place on a cutting board. Let stand for 5 minutes before slicing.
To make the sauce:
In a small saucepan over medium-high heat, whisk together the broth, apricot nectar or orange juice, and mustard. Bring to a boil and cook for 2 minutes. Combine the cornstarch and water in a cup and stir until smooth. Add to the saucepan and cook, whisking, for 2 minutes, or until thickened. Serve over the pork.
Serve this impressive pork dinner with a wild rice pilaf.