Whether or not to divide it will depend on what you find when you transplant it. Ideally, no, you wouldn't divide a second year plant. But if your goal is to transplant it into a planter, and you want to expand your hop yard, then I would divide it, assuming you have multiple rhizomes. You'll need to cut sections of the crown that have the buds/growth tips--a bare section of root won't generally work. It is amazing how little of a cutting can translate into a new plant; however, the larger the rhizome, the more stored energy there is to get things started in the new growing season. B-Hoppy, I believe, reported that placing these new shoots (the buds/growth tips on the rhizome) just slightly above soil level helped motivate their early growth (as opposed to burying them completely).
Worst case, you could plant your Centennial as is, and then purchase a few new rhizomes to expand the yard. Still, I am willing to bet that you can split what you have in two or three, at least. I've cut dozens of rhizomes out of one wine barrel planter in the past from a plant that was only several seasons old--it's amazing how they spread if they are cared for decently well.