I'd just like to start out by saying that kind of sheet music isn't only for guitar - it's for any instrument that plays in higher registers (e.g. violin, flute, right hand piano, etc.).
The treble clef is the first symbol on the staff (the name for the set of five lines the notes are on). A clef tells you what note each line/space on the staff stands for. Here's a diagram. You'll notice it goes in alphabetical order.
http://cnx.org/content/m10941/latest/TrebleClef.png
I'm not going to teach you where the notes are on guitar, because I'm assuming you already know.
The second symbol (#) is the key signature. A key signature tells you which key you're in. (If there's nothing there, you're in C Major or a minor.) There can either be flats or sharps there, but because there is only one sharp, that is telling you you're in G Major (or e minor, but I don't think it is). Here are the key signatures, if you don't already know what they are:
http://www.piano-keyboard-guide.com/images/music-key-signatures.GIF
That sharp in the song is sitting on the F line. That means every single F in that song is sharped as long as that key signature is in effect.
Wait do you know what accidentals are?
Sharp = one half step up (So... F# equals half step up from F)
Flat = one half step down (Gb equals half step down from G)
Natural = play written note and ignore sharps/flats in measure/key signature
http://upload.wikimedia.org/wikipedia/commons/e/e0/Accidentals.gif
The third symbol is the time signature. I'm not going to go over every single time signature. That (c) sign only means that there are going to be 4 beats in every measure, and that one beat would equal a quarter note. So that means four quarter notes can go in one measure.
http://www.piano-lessons-central.com/image-files/bar-measure.gif
Here is a lesson on time signatures. This will prep you for rhythm.
http://datadragon.com/education/reading/timesig.shtml
Here is a lesson on rhythm notation. This will tell you how to read the stems of the notes.
http://www.studybass.com/lessons/reading-music/rhythmic-notation/
Here is a lesson on treble clef notation. This will teach you how to read the heads of the notes.
http://www.musictechteacher.com/quiz_help_treble_clef.htm
The checkerboard symbols above the staff give you the chords you could also play with the song.
Here are some common guitar chords. I only play guitar a little bit, so I can't teach you how to play each chord.
http://people.bukiki.com/wp-content/uploads/2009/03/bukiki-guitar-chords.jpg
The symbol at the very end of the song is called a final barline. It tells you the song is over.
http://0.tqn.com/d/piano/1/G/j/E/-/-/GL_final-barline.jpg
Feel free to email me if something else confuses you. I am a huge advocate for learning to read sheet music. It's kind of like learning a different language - it's really frustrating at first, but once you become fluent, it becomes an integral part of your life.