Place pork in a 9x13 inch baking dish, and sprinkle meat with salt, pepper and garlic powder. Top with onion and celery, and pour wine over all.
Bake in the preheated oven for 45 minutes.
When done baking, remove meat from baking dish, and place on a serving platter. Pour gravy mix into baking dish with wine and cooking juices, and stir until thickened. Slice meat, and cover with the gravy.