The one in the link is just a single turn - most sailwinches do several turns (3.5 is common). For a large boat like yours I would suggest something with more travel.
If you want a proportional one, shop-bought is the way to go, but the bigger and stronger they get, generally so do they cost more. Some high end ones do need their own higher voltage, heavy supply, some of these contain a BEC (much as in many ESCs) to supply the radio and other servos.
Making a winch by modifying a standard servo is easy enough, but lacks the speed of a bigger, purpose built unit.
A powerful arm is simplest to rig, but does need very careful mounting and room for the arm to swing. A drum setup traditionally is more complex because of the need to avoid tangles with slack line. Mounting is easier because the pull is always in just one direction. The new breed of winches with captive drum technology are simplest to fit and rig, and are quite compact as well, but do need the right kind of line to work properly.
I've recently been using one of these -
http://www.componentshop.co.uk/45g-sail-winch-servo-4-turns-end-to-end-travel.html- 15" of travel and seems to work well, but my boat is smaller than yours.
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