In the USA
hourly rates for labor can run 85 to 110 per hour or more. This could take you 3 or more weeks of time and material.
Usually, refinishing an interior
is something that is better handled by the new owner themselves over time. Really, unless your boat
from 1981 has a near perfect interior
you will probably find more pressing needs that will deserve your money
IMO - don't factor the refinish into your buying