Do I need to unlock this iPhone4?

Last November 2010 I purchased two iPhone4's at an Apple retail store -- without the AT&T wireless contracts -- because there was a chance I'd be working overseas and wanted to have the option to select a reasonably priced local overseas carrier. The model number of these phones is MC319LL/A. I have no idea what the IOS or baseband are as these iPhones have been sitting in their boxes, unused, awaiting our move overseas. They have not been updated or even powered up.

Now that my transfer in imminent, I want to make sure these iPhones are ready to accept a SIM card from an overseas carrier and work seamlessly.

One iPhone user says the phones still have to be unlocked. Another says they have to be jail-broken before they can be unlocked.

A salesman at the Apple Store says that since they've never been activated on a wireless contract, that they're already unlocked and that I have to speak to our overseas carrier about making them operative.

All that I understand about these devices is that they want to be initialized via iTunes when first powered up.

I see sites like iphone-unlocker-pro online which seem to offer a simple, all-in-one solution but I am not entirely sure this is what I need.

I would think that what's required is to power up the iPhone4, initialize it with iTunes, update the software/firmware to current specs, and then unlock the device or prep it for an overseas SIM so it will run seamlessly in our new locale.

Can anyone offer a definitive answer and solution/procedure?

Thanks in advance...