I hear some of the G1G1 v2 xo's were shipped with an older build. No big deal! Check your version in 'About My XO'. If it's build 767 then you are up to date. If not, it's easy to upgrade in the Terminal Activity with the olpc-update 767 command. See the wiki or the Help Activity for more info.
The Fedora SD is an alternative OS/UI to the built in Sugar UI and should not need any upgrade, regardless of what build your xo ships with. You use one or the other, not both at the same time.
As a newbie you should check out the Help Activity, the Getting Started page in the wiki and User:AuntiMame, (she has some great tips). Also, you will want a Developer Key.
Have fun, but not too much!