[H] Win 8 upgrade

[Winterlight]

Back in December, when Microsoft had the promotional for Win 8, I 
bought a couple of  Windows 8 Pro upgrades... one with the download 
and one with a DVD. I haven't used them yet, but plan on doing so 
with my upcoming new build. I have read about the upgrade process, 
and the new rules that require a running previous version that will 
loose it's license, but I am not clear on some the details. Can 
someone who has actually done this explain a few things.

Say you have Windows 7 running on a hard drive. You put a new SSD  in 
the computer, and install Windows 8 telling it to install on the SSD.

Will Win 8 install clean and allow you to switch the boot drive to 
the SSD during the install process?

Does Win 8 install remove the qualifying version from the hard drive 
so you can't dual boot?

Will your previous Windows 7 key now be void even if it is a retail 
Windows 7 Professional key?

I have an old Vista and XP key that I could install and  use to meet 
this requirement,  if I have to, but I want to be clear on exactly 
how it works.
thanks
m