All safely related parts/labor have FREE lifetime warranty. All manufacturer, atleast Honda. It's the law. As long as it's OEM.
You mentioned if Honda will replace it if you car was in a wreck? You mean an accident? Shouldnt your insurance take car of this?
I suppose you dont really need to take the seat out to replace it. It's just give you more room. You should have atleat got the Service manual prior to taking it apart.