Well, I took all the parts out from the old, so I'm not sure what could be left from the old door other than a hole, but there was this little circle thing that didn't seem to go anywhere, and in the picture was just sitting there without arrows pointing it to attach to anything. I don't know what it is, but the door opens and closes and the lock locks. I'm calling it a success.
Thanks, cj, but I think I'm good.