Preheat your oven to 375 degrees F and place the rack in the center position. Grease a casserole dish with cooking spray. In a medium saucepan, combine the refried beans, sour crean, chile powder, garlic powder, and ground cumin. Stir until well mixed. Warm the bean mixture over medium heat until heated through, stirring every couple of minutes. Add half of the chips to the prepared casserole dish, then top with half of the bean mixture, half of the pulled pork, half of the cheese, and half of the tomato. Add the remaining chips. Then top with the rest of the bean mixture, pork, cheese, and tomato. Place the casserole dish in the oven and bake for 5 minutes, or until the cheese is melted and bubbly. Remove from the oven and top with chopped cilantro and green onion. Serve with sides of shredded lettuce, salsa, and guacamole.