Hey,
Just to easy your mind about the IELTS, if you're a native English speaker you won't have a problem at all. I didn't look at any study material, wasn't aware of the format and had no idea what to expect when I got there and my lowest score was 8.5/9. It's really very easy. If you have the time to study I certainly would put some time in but just so you're aware, it's a fairly simple test just to see if you get the basics.