You're totally barking up the wrong tree. There are a few composers on these boards, but for the most part, we are people who work with cameras and stuff.
You're going to want to look into MIDI sequencing. There are TONS of forums and bulletin boards for that. Also, you might just wanna stop by your local musician store. Guitar Center. You're going to have to spend money, but not much to get started. You don't need an instrument. There are softsynths and virtual instruments for that.