I'd go with everyone else's advice and build a completely new one. I've heard more cons than pros about prefab coops. Most of the ones I've seen at places like Tractor Supply look pretty cheesy, probably made in communist China (and I don't want anything from communist China if I can help it; their d**** virus is bad enough!). However, the ones made by the Amish look pretty decent if you could get hold of one of them. I wouldn't sell yourself short on your building skills. The run you built looks pretty nice.