Spray 5-quart slow cooker with cooking spray. Sprinkle taco seasoning mix over pork shoulder, pressing to coat. Place pork in cooker. Top with enchilada sauce.
Cover; cook on High heat setting 5 to 6 hours or until tender.
During last 20 minutes of cooking, make taco shells: Separate dough into 16 biscuits. Sprinkle flour on work surface; press or roll each biscuit to form 6-inch round. In 12-inch skillet, heat 2 tablespoons of the oil over medium-high heat. Add 2 biscuit rounds to skillet; cook 1 minute on each side or until light golden brown. Repeat with remaining biscuit rounds, adding more oil as needed.
Remove pork from slow cooker; shred meat with fork, discarding fat. Place shredded pork in large bowl. Strain sauce. Add 1 cup of the strained sauce. Stir well. Spoon pork mixture into taco shells. Top with salsa, lettuce and cheese.