Hi Michelle! Congrats on your new #1, and welcome to the party!
First, you need to foil the bottom of the smoker, as well as the lid to the smoke box. Be SURE to poke a hole in the foil for the drain/air hole in the bottom!
As for wood, 2-2.5 oz will be plenty for your ribs. These smokers require very little wood to make some great Q. Never more than 3 oz for baby backs. Mustard - yes! Then rub, wrap in plastic, let get happy in the fridge overnight. In the smoker @ 235, let them go to 4.5 hours with no "human intervention." Then, check for tenderness with a wooden toothpick. If the meat is tender between the bones, and they pull away clean, you're done! If not, go another 20-30 min and re-check.
Don't forget a mini-loaf pan full of apple juice or water for moisture! Set it on the bottom of the smoker, up against the smoke box.
Post some pics, and let us know if you have any more questions!