Here's how you can save a little money by doing the Purchase and Sale Agreement and the re-documentation yourself . . . assuming you have no broker, bank, or other mortgage interest involved.
First, get the Name and/or Official number of the vessel and get the Official Document info on line. Next, take this info and use it to fill in the blanks in a standard Yacht Purchase Agreement. You can find one of these online by doing a Google search for "Yacht Purchase Agreement." Pick one that comes in a PDF Format so you can fill in the blanks on your computer. Include names of purchaser(s) and seller(s), addresses, purchase price, boat name and official number, description of vessel, and attach a list of the equipment that comes with the boat, right down to galley utensils if there are any. No SS#s are needed here. Also list the contingencies of the sale, i.e. survey, financing, sea trial, etc.
Remember, with these online PDF files you can't save the document, so print out as many copies as you want. There should be one for you and the seller, and one for each and every buyer and/or seller, in the event there are multiple buyers and sellers. Each copy should be signed and dated by both parties, and each one notarized. Again, make sure you have all the agreed on conditions of sale, e.g. survey, loan, sea trial, things to be fixed, etc.
Now go to the USCG National Vessel Documentation Home Page and download the appropriate forms, first and foremost of which is the request form that will tell you what if any liens there are on the boat. This is the Abstract of Title request. Send this in first. You should have results in a few days. If there are any outstanding liens (preferred mortgages on the boat, these will have to be satisfied or released before a new document can be issued. Applications for Satisfaction of Mortgage, and forms for filing of mortgages, are also available on line at the link above.
For re-documentation, you need a notarized Bill of Sale, a Satisfaction/Release of Mortgage statement for each mortgage (signed and notarized by a bank official), an application for Filing of Mortgage (if in fact you're financing with a mortgage company or assuming someone else's mortgage), and the current Certificate of Documentation signed over to you.
All these blank forms are available at the NVDC Site listed above.
One final note: The procedure for documenting a new vessel is slightly different. You have to prove ownership and citizenship, which means you will need a builder's certificate and Form 1258, where you can provide your social security or tax I.D. number.