I'm not entirely sure about this, but I don't think you can get a "used" copy. As far as I know, each and every copy of ME3 is irrevocably bound to a single Origin account. So I don't think you'll be able to get one that isn't new. As for Origin, if you really want to be paranoid about it, set yourself up a separate partition, install some VMware, and battle your heart out to make things work in a relatively safe virtual environment. Personally, telling it to not start up automatically is enough for me. No matter what you do, though, you will need to have it installed and running to play ME3.
As far as unofficial endings go, I prefer this one:
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The Master said: "It is all in vain! I have never yet seen a man who can perceive his own faults and bring the charge home against himself."
>Analects: Book V, Chaper XXVI
As far as unofficial endings go, I prefer this one:
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The Master said: "It is all in vain! I have never yet seen a man who can perceive his own faults and bring the charge home against himself."
>Analects: Book V, Chaper XXVI