Juice oranges and limes and add olive oil to juice and mix.
Add the chicken to the Crock Pot and add juice and oil. Top with garlic, chili powder, cumin, oregano, salt and pepper and cook on low until tender, about 6-8 hours, or on high for 3-4 hours.
Once chicken is done, pre-heat the oven to broil and move a rack to the top slot.
Remove chicken from Crock Pot and place in a medium sized bowl. Use two forks to shred. Reserve about 3/4 cup of the sauce from cooking.
Add 1/4 of the sauce from the Crock Pot and give a good mix.
On a baking sheet / jelly roll pan (make sure it has edges), add the shredded chicken and top with another 1/4 cup of the sauce and add to top rack of the oven.
Broil until it starts getting crispy, about 5 minutes. Remove from oven, top with another 1/4 cup of the sauce and give a gentle mix. Broil again for another 5 minutes until chicken is crispy.
Remove chicken from oven and assemble the tacos. Lay out tortillas, spread with some sour cream, add the chicken carnitas, and then top with Pico de. Gallo and guacamole. Serve with the lime wedges and hot sauce if desired.