Hi, noob here

.
I'm looking to get my first kit for my mountain bike, and I've been trying to figure out some of the laws dealing with motorized bikes here in Washington State.
From what I've found, it looks like I would have to get it registered as moped, which would mean that I would have to jump through a bunch of hoops, including paying for a VIN to be assigned, in addition to the licensing fees. Is that true? Or is there something I'm missing, and I actually don't need to go through all that?