Sorry I don't run AIM.
1: Back-up important files ( I like to back-up certian preference files, graphics, etc.)
2: You can start-up with the All or Base extension set, but I don't.
3: Crank up the installer and off you go!
4: After I install a System I like to "label" the control panels and extensions. Then I know if an Application or game installs an older version at first glance!