Rainy days

Every other day my Yukon runs starts and drives like a champ. However when it gets wet outside it refuses to start. I had Auto zone run codes and they said it may be the cam sensor or crank sensor, I would have to find which one to find the corrosion. Well that's wonderful and all but I am obviously not a mechanic and I can't afford to be a whiner, so I'm here to ask simply where either of these sensors are located. So I can change them and move on with my life. :banghead: