Personally, I find it enjoyable to understand why things work, or sound certain ways -so I enjoy music theory. But it can get in the way if you start writing and playing in an academic mindset. Don't let theory overrule your ear. The best songs are the product of people who were moved by the music they were making... not just following mathematical rules to create pleasing sounds.

There are some really helpful, basic theory instructions at:
http://www.teachlearnguitar.com
in the 'Student Resources' section

Hope this is helpful,
MW