I don't think changing the wifi card will require a re-install...
As for the other part of your question about what to do when an action you take on your install goes bad: You need to understand what you're doing to your install. For example, what specifically a given option in Multibeast or Probook installer does... does it install a new kext? does it install a patched kext over an existing one? does it install new files in /Extra or somewhere else? Once you know what the options do, you can be prepared to undo them. To discover what things do, you either read documentation that describes them, or you look at the package in Pacifist (or both) and see where the files are going and what scripts are running in the package and what they do. If you're installing kexts via Kext Wizard, you know it is adding/replacing files in /System/Library/Extensions... Then you can plan to make backups for restoration later and/or be prepared to delete what was added. Of course, usually you then have to do such actions from another (working) install or by using Terminal by booting with the Unibeast USB. So, you need to have some knowledge of Terminal to go that route.
If you don't know what you're doing, you can make backups of your entire partition, so in the case of a bad change, you can restore the whole partition. Disk Utility can create disk images, and TimeMachine works for partition restores too.
As far as future OS X updates, you should probably wait for instructions from people here. When they come out, we'll look at the update in Pacifist to determine what might be the trouble spots and come up with ways to deal with them.