Welcome to Cruisemates!
D306 looks like a great cabin to me. You're between two passenger decks so it should be quiet. As AR said, I wouldn't worry about any noise from the lifts. It's nice to be so close to them!
Your balcony will be uncovered, but unless you're planning on something "interesting" you should be fine
I'd suggest you bring some Bonine (meclazine) or some ginger tablets for sea sickness "just in case".
Have a wonderful cruise! We're hoping to do this one in 2009