Windows 8 and Windows 7 share the same driver model. Windows 8 comes with a standard set of class drivers for common hardware devices. Usually, drivers that are preloaded with operating system offer basic functionality and you will need to go to the device manufacturers website for optimized drivers for the device, this includes devices such as your video card or printer.
Depending on the edition you are running, you can preserve your personal files, applications and settings. Regardless of that, I strongly recommend you dual boot with your existing operating system instead of replacing it with the Windows 8 Release Preview. The Release Preview is still under heavy development and you should not replace a production copy of Windows with it (whether that be XP, Vista or Windows 7).
http://techingiteasy.wordpress.com/2012/03/05/how-to-dual-boot-windows-vista7-and-windows-8/