Password needed for 3DS eShop?

Now that it's even cheaper, I'm going to buy a used 3ds. Now, if the previous owner had logged on to the eShop, but not linked their Club Ninty account, would I still be able to get the exclusive stuff? Or, if they de-linked their CN account before the 12th, but went on the eShop at least once more, would I still get access if I was lucky?
P.S. the place where I usually buy games didn't have one of those resetter-thingies when I got a DS Lite 2 years ago, and they're still really small, so that's why I'm curious.
P.P.S. I DID use Google beforehand, but came up dry.
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I did the smart thing and called, but the store doesn't have any used. if, by some freak chance people would exchange when the NGP comes out, would ^work if they exchange one from before the 12th?

it might work but the chances of someone keeping their account is very slim if they have traded it in but good luck tracking one down

if they were just trading it in for the NGP, would they really care about their eShop account, though?

im hunting for a 3ds aqua blue but the ambassador programme isnt important to me really since i got a black 3ds at the launch