What dies can I use with these machines?

Punches are good for wire or plastic binding.. There are different dies depending on what size your wire or plastic is. These are interchangable. There are also dies that put the holes in the middle for calendars to take the calendar hooks.

Do I need a separate machine to put the wire-o-bind in?

There are automatic machines on the market, these are quite expensive. These are only really good if you are going to do long runs. If you are going to do short runs you can get two seperate machine; a punch and a closer.

Can a punch be used to make holes for calendars?

Yes, it can.