i've recorded some guitar into garageband via presonus firebox and j-station,,,also some voice.
when mixing down, is there a way to eq in garageband with bass, treble, and mids, or is it basically only volume and pan.
thanks

Yes.
In the Track menu chose "Show Master Track"
Double click on the master track (it should be at the bottom of the edit window)
In the window that opens you will see many pre sets. If you open the "Details" slide you will be able to make your own settings,,, ie EQing and such. You should be able to make a decent master this way.