Can I Just Put My O2 3G Sim In A New iPhone?

[swanage]

My current O2 pay monthly sim is 3g activated.

If I but a sealed new O2 iPhone 3G from Ebay can I just put the sim card in and away I go?

 

[shoppy]

Yes you can you need to add on the iphone bolt on to get the data and just activate via itunes.

 

[swanage]

Yes you can you need to add on the iphone bolt on to get the data and just activate via itunes.

My current contract includes unlimited data and is used in my first generation iPhone so I guess I don't need that add on? What happens when I synch with iTunes then? So there is no need for me to jailbreak or any other. Real the phone? Is it really that easy?