I want ps vita so bad, but before that i have some question here:

1. Should i get 3g or wifi version?
Because i accidentally typing some keywords in google and i found that there are problems like "can't detect the sim card", etc

2. Can I run/play 3g version vita without insert the sim card?
Because i haven't plan to use the 3g service right now, and i will choose the 3g because "maybe" one day i will need the service.

3. And the last I need some advice where can I get good + cheap ps vita in KL?
Well, like 2 days ago i went to lowyat and there is a counter there sell the cheapest console. But when i check the 3DS red flare color,
seems like they changed the original chasing with the fake one. The color of top and rear doesnt match. yeah i can tell my house mate got 3ds.
Somehow it explained why they could sell cheapest there..
Therefore i need advice from the masters here.
Thank you very much

If i buy used vita with registered name/id

Can i change it to my preferable username/id?

Hmm.. I dont think any shop will take the risk to give their shop warranty.