Welcome to Cruise-Chat
A three night cruise will be a wonderful start for you. Cabin D114 is in the front of the ship. Not knowing your sensitivity to motion you may feel a little motion, then again not. You have cabin decks above and below you so you don't have any noise concerns from lounges, etc. It should be a pretty good location.
Since this is a 3night cruise I would think you would only have a carry on luggage. But if you do have a bigger luggage you will pack it the night before and set it out in the hall before you go to bed. The cruise lines will give you instructions in a daily activity sheet called "pitter patter". The ship should arrive at 7AM but you can get up and go have breakfast. The cruise line will also let you know what time and where you should go for disembarkation. Relax, the daily Pitter Patter will give you a lot of information. The ship has a Guest Relations desk you can always go and ask questions if you can't figure something out.