I just got back from my cruise on the 21st.....you are going to have a blast!!!
As far as the tipping goes, I didn't know how it worked either. When you get onboard, they set-up a Seapass card that works like a credit card. At the end of your cruise you can either pay it with cash or bill it to your credit card. I had my set-up with my CC right away and avoided all the lines at the end of the cruise with people settling their accounts. Everytime I used my Seapass, it was the same as using my CC. Sometime during your cruise, stop at the desk and charge your tipping to your account. On the last day or so of your cruise, your steward will deliver 4 envelopes to your room. They make it very simple for you and even address them. Then you just put your voucher in the appropiate envelope and hand it to the person when you see them. It is really easy.
The other thing is....everything on the cruise is easy. There are instructions for everything you want to do either printed in their daily newsletter or on their informational channels on TV.
Have a wonderful trip. I wish mine wasn't over!!