Hey...
When you make a song in garage band, make sure to pay attention to those little red dots next to the track descriptions. Those let you know when you need to EQ you're work lower. When stuff gets too loud, it clips (at 00:58 it clips BIG time.) If you want to accent stuff, try to lower the tracks that surround the lead. Also, you should always keep in mind how loud the master volume is. You see that lone volume indicator right above the midi creator, right next to the tempo device and right below the track editor? Try to keep the volume here as close to the yellow as possible.
Also, the guitars in garage band are all right if you know how to get the right sound out of them. What I like to do when I pull out the guitar is change the amp sim effect to the british overdrive. I feel like that sound is a little more true. Then, I'll turn off the echo and turn up the reverb. Dunno, it's just prefrence. Also, chords suck. Never play chords using the electric guitar preset, something I don't think you did anyways. meh.
You're melodies are great. I love them. You obviously play music outside of garage band. If there's really one thing I'd say work on, it's mastering, the drums were horribly mixed. If you ever want to colaborate, I can help you with the drums. I use garage band and I'm a drummer :P