Hello Sailor963. As just discussed on the phone if it's a case of getting the yacht into a suitable condition for Maritime to accept it as a tidy presentable boat and then they will transfer the mooring to you, the process as per Ramona's post above would be needed.
I have done this in the last 4 months with a yacht which was probably in a similar or maybe worse condition to yours.
Under Water Dive Services
www.underwaterdiveservices.com/www.underwaterdiveservices.com/about-us/were tasked to dive and scrape the very bad growth underwater. I cleaned the topsides and deck myself but it took many hours.
UWDS would be able to water blast the deck, cabin and cockpit and pump out all the water, clear the cockpit drains and do anything else needed.
I have no affiliation with UWDS - just know that they do a superb job.