I just purchased a iPhone from the apple store. It's still sealed. I have two questions, i hope someone can help me answering it.

1) If i unlock it with the newest unlocking software, will i be able to use my old Cingular/AT&T sim card plan (without having to renew a 2 year contract)?

2) I've been reading everywhere on this forum but i can't find the step by step on how to unlock a brand new iPhone using a Apple computer. Can someone link me to the right page where it has steps by steps for new people like me? It needs to have every little step included like how to jailbreak etc...

Thank you to whoever helps me.