Art:
I moved your original post to Yacht Systems, no problem.
As for working on the mast winch, I would work on it in place, BUT, I would cut a cardboard box and tape it around the mast under the winch as to catch any part that you may drop. When re-assembling the winch I would use winch grease that will hold all the paws in place. The winch grease is so sticky that it should do the job. That is the way I would do this.
Hayden