These threads may help you with the install:
http://www.rexnet.com.au/forum/index...howtopic=28191
http://www.scoobymods.com/forums/showthread.php?t=3791 (kartboy shift install, but is probably very similiar to the install of your GFB).
I recall seeing a GFB install thread once - maybe its the Kartboy link above that I am thinking of?
Good luck.