2. Go to the home page of your chosen distribution and read the instructions, or search for "how do I install <distro name>" there are lots of instructions out there. With many distros it's insert disk, follow the prompts, wait 20 minutes and reboot.
3. Yes - search for "dual boot linux vista"
4. Yes - it's called dual booting
5. Yes, but you will need to reboot to switch. Otherwise look at virtualisation - running one OS inside another.