Wow, you have many questions. Each can have a rather long response.
1. Installing Vista is simple, just put the CD in the disc tray and start up the computer. The install program will guide you the rest of the way.
2. There are various upgrades in Vista as opposed to XP SP2, mainly related to security, user interface, and performance...among many others.
3. I'm not entirely sure of what you are asking with your last two questions.
Here is a great resource for Vista, it will explain many of its features and installation to you.WinSupersite: Windows Vista