zooming ... either 1) mouse scroll wheel or without selection on, press shift+lmb (if i remember right, might be ctrl or alt)
backfaces are faces which face away from the current cameras point of view, its like if you put the palm of your hand infront of you, you can't see the back of it and that'd be the backface of the hand
to create a forward face in milkshape place down 3 vertex and then use the face tool and click on them in an anti/counter-clockwise motion ... for a back face click on them in a clockwise motion.
e.g
if you made them like that a front face would be
1,2,3,1 and a back would be 1,3,2,1