Ok, sneak by the three guards at the start of the level, stack up the boxs by the fense, crouch and sneak by the g-dogs WITHOUT waking them up, silently take out the two guards by the power generator, choose to go over either the left or right fence, when you see the door with blue thing in the middle of it sneak over to the left side and deactivate the power generator on that side, take out any guards silently if you can, go over to the right side and deactivate that power generator, go into the door that just opened up for you, use the all-excess terminal if you need to, use the boxes for cover and sneak over to the computer terminal, match up the code, and your done with Banner.

Hope this helps you out.