I had to go through the same about 18 months ago when I bought Valkyrja. PO had a large logo on both sides of the stern as well as the name and hailing-port on the transom.
I used a travel hairdryer to gently heat up the vinyl and peeled it off using a plastic 'spatula' thingy...the ones you use for spreading putty etc. No scratches or other damage of any kind. Took some elbow grease, but once heated, the vinyl could be largely peeled off in large flakes.
Removing the residual adhesive was a heck of a job though. I tried everything, including acetone, until I hit on the idea of using 'black streak remover
'. I sprayed it on and left it for a minute or two (can't remember the instructions on the bottle) and it came right off simply using the same plastic spatula-thingy. Then a generous scrub with nice soapy water and we were as good as new.
Of course, the gelcoat under the vinyl is lighter, but after a nice polish in the yard it's hardly noticeable.