Cook the diced potato in water over medium-high heat for 8-10 minutes until soft but not mushy. Toss with next 9 ingredients.
Heat oil in a skillet over medium heat, then lay 1 tortilla in skillet. Place filling in one-half of tortilla and fold over, pressing to adhere. Move quesadilla to center of skillet and cook for 4-5 minutes (turning halfway through) until cheese is melted, filling is heated, and tortilla is lightly browned. Cut into thirds and serve with sour cream and salsa. Repeat with remaining filling and tortillas.