Spent many years in the SW Pacific and more time than I like to remember steaming between islands. All parts of the Pacific can at times get rough but I would not say that they are treacherous. Indeed the Caribbean has a far worse reputation for sudden unpredictable bad weather.
There is nothing to be scared of (IMHO) I have been in the very worse that the Pacific can throw at you and the only bad thing that happened was that I spilled my Gin & Tonic and had one of the show dancers (female) fall in my lap during a large roll - As to the ship, she was only 30,000 tons.
Go for it, even if it does get a bit rough (not saying that it will) the ships are designed for it and it can be quite exhilarating.