Italian Sausage Stuffed Shells

Ingredients (6)

• + 1 (16 ounce) package jumbo pasta shells add to pantry
• ✓ 3 teaspoons vegetable oil, divided
• + 1 pound bulk Italian sausage add to pantry
• + 1 (16 ounce) package finely shredded mozzarella cheese, divided add to pantry
• + 1 teaspoon dried Italian seasoning, plus more for garnish if desired add to pantry
• + 1 (24 ounce) jar prepared marinara sauce add to pantry