In A Large Skillet, Saute Chicken In Oil Until No Longer Pink; Drain And Set Aside. Coat Skillet With Nonstick Cooking Spray. Saute Mushrooms, Green Pepper, Onion, Celery, Corn And Garlic For 6-8 Minutes Or Until Vegetables Are Tender. Add Salsa And Reserved Chicken; Heat Through. Serve Over Rice. Top With Cheese And Sour Cream.