I would say:
1. Your catch rate will be somewhat lower than that which you experience in the Summer months.
2. Not necessarily, a lot will depend on the conditions on the day, I have had successes on a relatively warm day on a dry fly.
3. I would kick-off with a Black Buzzer, Montana Nymph, Diawl Bach in all its variation and smaller versions of a baby doll maybe. also never leave home without a Pheasant Tail Nymph and a few different sizes of Shrimp or Czechs. A few good lure patterns are a good bet too.
Use a good intermediate or sinking line and a slow retrieve, figure of eight method, as the Trout won't want to chase too quickly.
Depending on the conditions the fish can be at any depth but start out as deep as you can and work upwards on successive casts and try to find the depth they are laying at. They can even [FONT="]take emerging insects, such as chrinominids, which are active all year round.[/FONT]
Don't forget to wrap up warm with several layers too, once the sin gets low it gets pretty cold.
Good luck