Hi Aaron,
Good starting calorie would be basic metabolic rate plus 500 Cal. You could estimate your basic metabolic rate by multiplying your weight in lbs by 13. Monitor your weight gain, and if it is very minimal or too slow, gradually increase this figure.
Diet needs to focus on eating a lot!! Ensure you don't consume less than 20% of your energy as fats, as below this figure your testosterone is weakened. Naturally choose good fats such as flax seed oils, nuts, seeds, hemp seed oil. Most health shops sell an optimised oil solution that you take off the spoon. Great for muscle gain. Definitely take 1-1.5g of protein per pound of bodyweight at least and match that again with the same quantity of carbs. Be sure to eat protein every 3 hours (awake that is, though bodybuilders do get up in the night for protein shakes. May be a bit extreme in your situation though). Aim to consume at least 6 meals a day with protein/ carbs in every sitting.
Shakes. Just go for good old whey powder.
Exercises. Concentrate on powerlifting techniques, such as bench press, deadlifts, squats and avoid small weight lifts. Lift heavy 3 times a week for no longer than 45 minutes a session, and spend the rest of the week doing as little as possible. Work in the 8-10 rep range for 3-4 sets. 3 different exercises is more than enough if the intensity is high. No CV, no stress, just pure relaxation.
Creatine. Yes, it is definitely worth considering. I would suggest training hard for 3-6 months before using it to get your body to the next level. Take it too early and you may not be training with the intensity to make the most of it. It basically enables you to store more resources within the muscle to crank out an extra couple of reps, and more force when contracting. (Not the technical answer, but you get the picture).
This is the standard textbook answer, though like all situations it may need tweaking for your personal circumstances.