We've got two different sizes, on the 44.2st the main shaft comes out by undoing a couple bolts, which splits the center stem from the base. On the smaller 40.2st, the entire winch is unbolted from the deck. Either way, should be obvious from looking at it once the drum is off.
Unbolting from deck is easily done, thanks to the bolts being threaded into glassed in aluminium plates, so you don't need a second person to hold nuts and backing plates inside the boat or remove ceiling panels. Apply a bit of grease on the mounting bolts so they don't corrode and come out easy next time.