Camping is EASY. They open up a big chunk of downtown Centralia for camping, they open up the gym at the community college for showers, and for a fee, Cascade will ship your camping gear there for you. We've stayed in a hotel three times and camped once. I actually enjoyed the camping year quite a bit. (Of course, it didn't rain at all - that might change things a bit.)
As for the route, there are a couple of short climbs, but nothing sustained to speak of. If you do it in two days (as the majority of riders do) think of this as more of a parade celebrating cycling than a major ride. It is kind of like a mini Ragbrai.