My last boat had state
registration when I purchased it. When the
Marine Title Company looked it up by
Hull Number in the USCG list, they found that it had orginally been documented. It seemed the previous owner was not American and couldn't document the boat with a green card.
Anyway, it was nothing to re-document the boat using its orginal Documentation Numbers. As I
recall, it was less than $500 including the Title Comapnay
fees.
You can do it yourself, but in the long run it might be easier and faster to hire a
Marine Title Company.