You won't necessarily have iLife - it comes with new machines but not with OSX when purchased separately and who knows what the previous owner has done. However, you can get the individual apps through the Mac app store, which you should have with Lion. 'Office' types apps are not in iLife anyway, they are in iWork, but they too are available separately.
If you need/want to run windows software you can do it from within a 'virtual machine' but for that you need the virtualisation software (e.g. VM Fusion or Parallels) and Windows itself. These are mac programs which allow you to run windows. Alternatively, you can use bootcamp, which does come with your OS, (you will still need a copy of windows) - this allows you to boot your macbook air into either OSX or Windows.