Congrats on your B2B Cruise, and Welcome to Cruise Reviews Forums!
Dave explained it perfectly for you. I'll just add that they will lead you off the ship as a group to go through customs and re-board. Usually a smooth and quick process. About the Soda Program, you will have to purchase another one for the next cruise. In theory you could flash your old card with the sticker. That would be un-ethical though and they would know as they'll check the card the first time they serve you. Not saying that is what you had in mind. Just squashing some rumors I read elsewhere.
You asked for some other suggestions for a semi-rookie cruiser. I am sure you will get some.
Have a great time on Carnival Magic, and Welcome Aboard Here,