Yeah, as frustrating as it definitely would be for you, I can't see where the seller has done anything wrong here, in fact it does look like he has tried to be helpful in arranging for the repairs for you at the expense of his time.
That sounds like pretty good after market service to me, and after that he didn't have to inform you regarding using second hand parts, although I must confess that I don't understand that at all. If the camera was new, well 13 months old, and they could find second hand parts, why couldn't they find new parts...that sounds bizarre!
Anyway, the point was he did ask you regarding the second hand parts and you said no. I'm not sure what else he could have done at that point, but return it to you....most likely also paying the shipping to his repairer and then returning it back to you.
So he has invested his time and some money in trying to resolve an issue for you when he could have just turned his head and walked away.
I'm getting the feeling that you are writing out of complete frustration, however I think after you settle down and gain some perspective, you may well see the situation differently.