Cook the lo mein noodles (or spaghetti) as per the package instructions. Drain and set aside.
While the noodles are cooking, heat the oil in a wok or large pan over high heat. (Note: You will need a pretty big pan or pot. I use a 12-inch chef's pot that is shaped like a wok and holds about 5 quarts). Add the chicken, season lightly with salt and pepper, and stir-fry until cooked through, about 5 minutes. Remove the chicken from the pan using a slotted spoon; set aside.
Add the snow peas, carrots, celery, bell peppers, onions, mushrooms, ginger, and garlic to the pan. Stir-fry just until the veggies are crisp-tender, about 5 minutes. Reduce the heat to low.
Return the chicken to the pan, and add the noodles to the pan.
Combine the soy sauce, sesame oil, and oyster sauce in a small bowl and add to the pan.
Toss everything together to combine and coat the noodles evenly with the sauce. Cook until heated through, and enjoy!