I just rebooted my air when I got it a few weeks ago. When you reset it, its gonna ask for your apple ID and password and you have to have bought ML through your account. If not then you need to use somebody else' macbook because they have the app store on it, sign in and buy it through there and you can't use the app store at apple stores for some reason because it doesn't let you sign in. If you already have it though and its through your apple account then you're all good. I'm pretty sure you would lose your office because its going to factory settings which doesn't include office.
Yeah the thing is though, I don't know how exactly mountain lion got on there(not that I'm complaining; I'm not as familiar with Mac OS though

) I'm sure it was installed but how? anyways, I haven't ever logged on with my apple ID on my macbook (ml was already there when I got it.) How do you install ml from one macbook onto another?
EDIT: wait, so once I purchase ml with my apple ID, I can install ml on any mac that I'm signed onto with?