As you can probably tell from the title of this post, I'm a little new to this. That said;

-Do I need to unlock my iPhone before I begin applying skins, modding, etc (using FuGu or similar)?

-If I use the program "Jailbreak", does this SIM unlock my iPhone or simply App unlock my iPhone?

-Finally, if I use a program such as "Jailbreak" (etc), will it allow my iPhone to update with the next release of iPhone firmware?

Thanks for any help!