slutgarden: billy sheehan knows loads about theory dude go buy his books and dvds..but i mean he don't really talk much about stuff IMO you don't need to know like all those italian words violinist,pianist etc. ,names of the modes(but he shows you how to play them), etc..
i just learn the stuff that i feel would help me musically like scales, chord theory and stuff. Scales and chord theory to me are really important, maybe they'll help you, go explore a lil