Congratulations on your first cruise!
What to pack? Not as much as you think. Think casual, T-shirts, shorts, sandals, and bathing suits.
Decent pants and shirt for the dining room (no shorts or jeans), and at least 1 "formal" suit and tie for formal night. Comfortable shoes for walking the ship and on shore excursions.
Dance Lessons? Yes, watch the daily schedule of activities (delivered to your room) for all kinds of dance lessons, line dancing, tango, hip hop, many ships offer many different kinds of dance, usually by the entertainment staff.
What to look forward to? Lots of fun! Depending on how far you live from the port of departure, your flight may be a bit uncomfortable for your height, but you'll survive. Get up and stretch when you can. May I suggest if you're flying from a wintery climate, GO A DAY EARLY! If there's a storm, you miss your flight and you miss your cruise. As for the cruise, you will enjoy the relaxation of everything being done for you. Your room is cleaned daily, your meals are served to you, and there is entertainment galore on board. also check the daily schedule for singles get togethers.
DC Plug? 110 universal, if you are from the U.S. or Canada. If you are from the U.K. you might need an adaptor.
Hope that was helpful, enjoy your cruise!