I apologize in advance if this question sounds stupid. I have just won on eBay a new ipad 2 WiFi only. Does this means that I can never upgrade to a 3g cellular connection on this ipad 2 ?

Correct. If it is Wi-Fi only it cannot be upgraded to 3G at least natively.

Correct,you can't add cellular capability to an iPad that was manufactured without it.

Ok, thank you

But you can add a myfi to give you a mobile wifi hotspot to connect your iPad.

The Archangel

You can use either your mobile (cell) phone or a "wireless hotspot" to connect to 3G. The procedure (called tethering) is to connect to the device by WiFi and use it's 3G network.

Advantages include one less mobile bill (if you use your phone) and the fact that you can position the device for better reception, e.g. near a window. You can also share the connection (and account) with other devices such as your notebook.

Disadvantages include, one more device to charge (if using a hotspot) and no GPS. Apparently Some carriers do allow tethering.

Check your data plan before doing this.

You might try explaining it to someone at an Apple store and they my exchange it for a different model is you are lucky. It is worth a try, and you have nothing to lose. It depends on the iPad condition when you take it in. They will check it to make sure it is not hot, and not tampered with.