Can I put my SIM card in an Iphone? - 1

So I want to buy the Apple iPhone 3G 8GB online to replace my old phone. However, Tmobile is my service provider and I have a Tmobile SIM card. Tmobile runs on GSM and so does this Iphone I want. If I put my sim card in the Iphone, will it work? Will I be able to use the internet as well?

-Thanks, answers are appreciated.

Yes t mobile sells them now or go to the mall and the cell phone booths cut them for like 5-10 dollars

and it works the same juse depends where youre at
i have an iphone 4 with t mobile and it works sucky where i live but when i'm by the free way it works better