Preheat the oven to 350°F Coat a 9 x 13 baking dish with nonstick cooking spray. Cook the shells according to the package directions; drain.
In a large bowl, combine the ricotta cheese, 2 cups mozzarella cheese, 1/2 cup Parmesan cheese, the eggs, parsley, garlic, salt, and pepper; mix well.
Spread 1 cup of the spaghetti sauce evenly over the bottom of the baking dish. Spoon the ricotta mixture into a pastry tube or large resealable plastic storage bag. Snip off a corner of the bag and squeeze about 1 tablespoon of the cheese mixture into each shell; place filled shells in the baking dish.
Pour the remaining spaghetti sauce over the filled shells, cover with aluminum foil, and bake for 40 minutes. Remove the foil, sprinkle with the remaining 1 cup mozzarella cheese and 2 tablespoons Parmesan cheese. Bake for 10 to 12 more minutes, or until the shells are heated through and the cheese is golden and bubbling. Let sit for 10 minutes before serving.