clipped
Very good diagrams. I'm sure there is something I am missing, but.....can you not prop something behind the wheel to hold it whilst you screw the door to it? Even a strip of cloth around the back of the wheel, insert wheel into track, have someone hold the ends of the cloth to start the screw, pull the cloth out when the door is in place.
I don't usually have problems putting stuff together after I have taken it apart, unless I drop a part whilst looking for a tool. My worst habit is putting important parts in a very safe place until I can make repairs, then forgetting which safe place I put it in :o)