If you've never used Linux before, don't worry. It's just as easy to use as any other operating system, and in many ways, it's easier. There are no drivers to chase and new applications are always installed through the Linux equivalent of an app store. And, as you're going to be installing and using Linux on your Raspberry Pi, it makes good sense to create your SD card from within a Linux environment.
It doesn't make the installation any better, but it gives you a great opportunity to try it out before plugging in your Raspberry Pi. We recommend Ubuntu, as it's ideal for beginners, but these instructions will work for nearly any other version of Linux – replace the Ubuntu Software Centre with your package manager of choice and ignore the desktop specifics.