Mine lived out all winter with minimal shelter. In your area they'd need some protection... a place to get in out of the wind and wet. They are not as waterproof as N. American ducks. My understanding is that the cold is little trouble.
I can't lie...their poop is pretty nasty. All ducks are pretty much.
Here is an article I saved on them some time ago. I got my muscovies from this hatchery and actually spoke to this fellow. He was very nice to talk to.
My neighbor has guinea fowl. For some reason they just peck at my glass doors all day though. In all seriousness I do think they have helped with the ticks a bit. They are beautiful too. Though not quiet.
FWIW when I was a kid I was chased several times and ultimately attacked by my parents' muscovy duck. I don't remember it, I might well have been to blame, but it was enough for them to eat it and move onto other types.