Though many great guitarists claim they have no knowledge of Music Theory, I don't think that's a good reason not to learn something that can really be useful to a musician.
Some say that it's too difficult to learn and others say they don't want their creativity to be harnessed.
Like every kind of knowledge, if we let it dictate all of our actions, we will lose our creativity: a song composed following only harmonic rules (or 'commercial' rules, for that matter....) will sound more like an exercise, quite dull, uninteresting.
But if we combine heart, ear and theory we can go beyond our limitations, we can understand our Art better and generally save us a lot of time and trouble. We can find easily that perfect chord we were looking for, or try some different ones we would have not come up with just by chance or ear.
If you plan to arrange or produce your own material, music theory will be an invaluable help.
And if you're worried about it being hard to learn, don't worry: if you can count to 20 and add 8 to 8 you' re over-qualified for the task.
If you keep your ears open and a guitar nearby, it will help a lot.
We're gonna learn about Scales, Chords, Modes, Keys and all that jazz...
We will begin our fascinating journey in the world of Music Theory starting from Intervals...