Question about setting distortion level in GB

Hi! I am using GarageBand on an ibook, so I do not have the type of outlet necessary to plug my guitar directly into my computer. As a result, I am forced to record chord progressions manually through my internal mic and I can never a get good sound from my electric guitar (nothing but static, go figure). Anyway, GarageBand does cooperate with my acoustic guitar, and I have found that I can use the "distortion" option on the track to make it sound more electric. My question, then, is how I can adjust the track settings to get the best, most crisp possible sound, bearing in mind that I am trying to make an acoustic guitar sound cleanly electric. Thanks so much!