I have background in music, how easy is it to learn guitar?

I play the flute as a freshmen in band, and I have been playing the piano for about 2 1/2 years now. I 'd like to start working on learning the guitar this summer. How difficult on a scale of 1-10 would that be? I can read music so that isn't a problem. and I can reach an octave on the piano. I don't know if that information is helpful at all. Oh, and I won't be taking lessons from an instructor. I'm going to do it on my own by a book. So also if yo have any suggestions on which books to buy or which websites to look at I'd appreciate that.