and it looks pretty simple but my question is if I want to do the trial of win 8 because i want to see the performance diff on it for bf4 from win 7 so my question is all my data going to be on win 8 when i load it or will i have to reinstall all of it again?
Since your Win8 install will be on a new partition or new drive it will be a completely clean install with none of your files or programs. You will see your Windows 7 partition or HDD when your booted into Win8 and you should be able to access whatever files you want, but you would have to re-install programs.
If you install Windows 8 over top of Windows 7 you will generally keep most of your system settings and files. I prefer a fresh install though.