Remove tails from shrimp. Place in a resealable bag with spice packet. Shake to coat. Heat oil over medium-high heat in large skillet. Add shrimp; cook 2 minutes, turn and cook 2 more minutes til shrimp is opaque. Remove from heat; cut into bite size pieces, set aside.

Heat refried beans in microwave until hot. Warm tostada shells in oven. (Be careful they burn easily).

To assemble tostadas: Spread each shell with a layer of refried beans. Layer shrimp, salsa, guacamole, sour cream, queso fresco and shredded lettuce.

Serving Ideas: Serve with spanish rice.