Garage Band, MBox, Audiophile confusion

[E. Bond Francisco]

Folks,

I'm a compulsive shopper. I have a G4 DP 800 Quicksilver, 1 G memory, 
and on that machine I have:

1) Garageband
2) Soundtrack
3) Protools
4) And somewhere, I think, an older version of Digital performer
5) FinalCut HD

For hardware I've got:

1) MBox
2) Audiophile soundcard
3) Griffin IMic
4) Cambridge Soundworks desktop speakers
5) An old Yamaha keyboard with midi-ports
6) Shure and Audiotechnica mics
7) ARTTube MP Tube Mic Preamp
8) A 30 year old warped yamaha acoustic guitar with a Barcus Berry 
pickup that you stick on the sound board with bubble-gum
9) And a couple of recorders, one alto, one soprano

My 10 year old neighbor showed me how to use GarageBand the other day. 
Vunderbar! So cool! And yet, um, I can't figure out how to hook up a 
microphone, or what to hook it into so that I/we (the neighborhood 
kids) can layer our voices into the music.

Where is the mountain-top dwelling guru who can direct me to a place of 
peace with all this stuff so that I might know how to actually do 
something creative with it? Any pointers to sources of knowledge 
greatly appreciated.

Thanks,

Bond