Teach me how to get baby ducks! I know nothing!

I currently have 4 females and one male. It is winter and so they are only laying about one egg every few weeks but I want to get my info now so I can have babies in the spring. I have one female that was broody last year before I even had a male and I would by all means prefer to have them raise the ducklings instead of me.
I just don't know what eggs to collect and what ones to leave if she does get broody again? Or if I do collect them to incubate when do I have to get them. How will I know if the egg has died? Also how old do the ducklings have to be before you can give them away. Also I really enjoyed getting eggs this last summer, will I still have to worry about chicks growing in them all year around? Even if you can only answer a couple of my questions, anything helps!