If it is documented you go to the CG documentation
site and follow the directions for name change & send $$. I can't remember how much but it was not too bad (5 years ago).
If the PO didn't follow through on his name change in officialdom, it is still on the books
as the old name. They may have let the CG documentation
lapse. I don't think most states cares what you name the boat.
We spent more on the champagne & food
for the re-name party. You don't need to hire a documentation service
. This can be totally DIY. BTW there are lots of fun sites to help you through the procedures & incantations to appease the sea gods. We wrote the old name on an 'ingot' of aluminum
using dry mark pen and hurled to to the sea - add some wine and magically, Neptune erased the name from his ledger.