1. Yes you will.
2. Most common are no drivers for some hardware. With the list you provided, no one can tell if you'll have an issue.
3. The machine's bios has to be current as well. Some are scared of this and end up with unstable machines. A good time to do this is after you have what you can't lose on your BACKUP media.
4. Backup? Yes. Changing/installing an OS is not without danger. The hard disk data and programs can vanish.

Bob