Heat 1/4 cup olive oil in a small skillet over high heat until very hot. Add one corn tortilla and cook until starting to crisp (about 1 minute); use tongs and turn over. Cook just until crispy. Place on paper towel to drain. Repeat with remaining tortillas.

Heat the remaining 1/4 cup olive oil in a medium skillet over medium heat until hot. Add the mushrooms and onion; stir in Mexican seasoning. Cook, stirring occasionally, until mushrooms and onion are soft. Stir in shrimp and cook just until the shrimp are heated through and seasoned. Add more Mexican seasoning and salt to taste.

While the mushroom and onion mixture is cooking, spread 1 tablespoon of the cream cheese on each cooked tortilla. Top with 1 tablespoon of the guacamole. When the mushrooms, onion and shrimp are done, place equal amounts on top of each tortilla and top with shredded cheese, salsa and lettuce.