thank you.
one other question. is the process any different if i want to jailbreak and unlock an iphone 4?
Ease of jailbreak would depend on the iOS version currently on the phone. When talking about jailbreaking, you can have a "tethered" or "untethered" jailbreak. Essentially, if you are using a "tethered" jailbreak, you will have to plug the phone into your computer and re-run the jailbreak program (i.e. redsn0w) every time the phone is rebooted or the battery dies. For example, if the battery on your iphone dies, you will have to plug it into your computer and re-run redsn0w or the phone will not boot.
An "untethered" jailbreak means that once the phone is jailbroken, you can turn it on and off at your leisure without having to re-run the software.
If your iPhone 4 is running iOS 4.0 or 4.1, there are untethered jailbreak solutions. Currently your only option for iOS 4.2 is tethered.
Once the phone is jailbroken there's no guarantee you'll be able to unlock it. This will depend on the baseband version of the phone (modem firmware). You can find this by going to Settings -> General -> About. Check this before you even jailbreak. If you're fortunate enough to be on iOS 4.0 with the 01.59.00 baseband, then you should be able to jailbreak iOS 4.0 or 4.1 using pwnage tool, which will also allow you to preserve the 01.59 baseband (this is what I have done personally). Once jailbroken with the 01.59 baseband, then you should be able to unlock using UltraSn0w from Cydia.
If you are not on modem firmware 01.59, then there is a (so I've heard) rather UN-stable unlock that involves creating custom firmware with the iPad baseband. I haven't heard many good things about this unlock, and as you seem rather new to the JB scene, I would recommend avoiding it.
I tried to keep this as high level as possible. I'm currently jailbroken on iOS 4.1 with the 01.59 baseband, so I've gone through the process I described above. Before you try anything on your iPhone 4 I would recommend reading through all of the stickies in the iPhone hacks section very carefully so you know exactly what you will be doing before you do anything.
In summary:
iOS 4.0 + baseband 01.59.00 = untethered jb to iOS 4.1 custom firmware using pwnage tool and unlock using ultrasn0w from cydia
iOS 4.1 (non-custom FW) = untethered jb (limera1n, greenpois0n or pwnage tool) and possible unstable and irreversible unlock using iPad baseband
iOS 4.2 = tethered jb using redsn0w, and possible unstable and irreversible unlock using iPad baseband
Anyone please correct any misinformation I may have provided. This was all based on my own understanding and experience.
NOTE: when I said "irreversible" in reference to the iPad baseband method I meant that no matter what you do you will not be able to change your baseband back to an iPhone baseband and will have to rely on custom firmware as long as you own the phone. This means if a new or critical software update were to come out, you would not be able to upgrade to it until the dev team releases a new way to create custom FW for that version of iOS.
It also means any damage caused to your phone using that unlock method would be irreversible unless the dev team can come up with some kind of software fix. Basically your phone would remain hacked for life, not out of choice, but out of necessity. It will also void your warranty should anything go wrong, and there would be no way to hide that fact from the geniuses as your baseband would clearly display as an iPad modem firmware.
