Composition teachers are very much an asset. I've been studying with one for about six months now and he has greatly affected my ability to compose. Everything from learning about my own compositions, how to approach them, what to look for, ect... to learning about other compositional styles/languages... tonal, atonal, polytonal, counterpoint, inverted counterpoint, dissonant counterpoint, harmony, extended harmony, seralism, set theory, experimentalism, etc...
Now i stress that I learned ABOUT these things, and dont really have comprehensive knowledge of all of them, but the fact is, six months before I had no knowledge of more than half of these things...
I would say go for it... there is nothing to lose.
Becoming involved in getting a teacher... someone who can help you with problems, whose struggled with them as well, someone who can share knowledge... only ensures that you are doing everything possible to becoming a better composer.
