Mine was built by a man (my hubby) so no plans were involved
But I can say that there are a ton of easy coop plans out there. (not o suggest you go to another forum but they have a TON of plans) try
www.backyardchickens.com Hope this helps! You can also pick up just about any chicken magazine at barnes and noble. They almost always have different plans. But some of those can get very elaborate.
As far as cold winters, as long as you can close them up at night but leave ventilation at the top. Keep bedding in there and use the deep litter method, the will do just fine. Also keep feed and keep them hydrated! That's how they regulate their body temperature.
Good Luck!