Natalie, when we first moved back to the U.S. we were in Washington and I went ahead and used the service at Legal Zoom to process the paperwork I needed. When I did the math and realized how much time and stress it would take me to handle it myself I landed on the side of paying someone to do it for me. At the time we had just moved from abroad and I was pregnant, trying to find a rental house, etc. etc. -there was a lot going on!
Now, we just moved to Portland, OR this past summer and I went ahead and did the paperwork myself this time. That included closing the business in Washington. It was a LOT of work, but well worth the effort and I definitely felt more empowered having done it myself.
With all that said, have you checked the info on the Washington Sec'y of State website? There's plenty of great information there. I will also mention that the few times I had a question about our small business forms or taxes I always found very helpful people at the other end of the line when I called in for help.