I thought about those questions too. My answer would be nothing. I feel, after losing two cats recently, that they simple sleep away. I feel the process of dying is what hurts me the most. I can't possible feel or understand the pain or piecefulness of it, i don't know if it hurts the person (or pets) as much as those watching.

I doubt this is of any help, or if it even makes sense. I'm having a hard time myself and dont know if I make any sense.