This topic comes up every couple of years, and I've experienced a lapse of Documentation on my boat, which costs extra, so here's what I did, FWIW.
I had received letters from Documentation Services - don't be duped, as there are dozens of these - who told me in so many words, "We walk you paperwork thru the NVDC, and we get your Documentation updated much faster than you can on your own." My BS detector was dinging constantly at this, so I called the NVDC very early one morning. They get totally inundated starting around 8:30, and you'll get their voicemail if you call later.
The lady at NVDC was very helpful, and told me exactly what to do, how to do it, and BTW, you can fax forms and even ask for special handling, or expedited handling. Ask about this when you call them. I was told by this Lady at NVDC that the outside 'services' do exactly what anyone can do, and that they have NO ABILITY to move you through the system faster, or easier; they have one business proposition only, and that's to take your $$$.
So, I sent my forms in, paid via credit card, and voila, I had my renewed Documentation in 2 or 3 weeks.
Don't forget, one new service is a TWO YEAR Document, simply pay two years worth, and you won't need to do this for two full years.