That's pretty much what we have too, but I wish we had the steel door. I'll have to look into that. LOVE the automatic door. It would save so many "did you close the chicken door" moments or trying to get them back in if we won't be home in time. Do you know what brand you have? Is it solar powered or electric?
I got the Ador1
http://adorstore.com/products/ador1-automatic-chicken-door
It runs off a lantern battery, so no electric. It was SUPER easy to install, and the only time it didn't open/close was when it got iced over (which I can't really blame the manufacturer for). The lantern batteries are cheap. I'll probably replace the battery once this summer, and I replaced it every couple months in the winter because I figured the cold weather would drain the battery and I didn't want to worry about it. There are cheaper doors out there that run on timers, but I like that this one automatically senses the light so it automatically stays open later as the days get longer. It also averages the light for a 5 minute span, so headlights or a flashlight hitting it won't open it. The chickens are clamoring to be let out in the morning, so it opens a few minutes later than ideal, but it stays open for PLENTY long at night, they are always in well before it closes itself.