you must take the glass off to gain access to the midframe and the back of the home button..the flex is "L" shaped and goes through a small opening in the midframe to stick onto the back of the home button. the other portion makes contact with the top of the dock connector. You can't gain access without lifting the digitiser/glass off. sorry. as for a guide? it's on a "to do" list.. if you follow the guide for the digitiser to the right you should be fine, it reallly is pretty self explanatory once you get to the home button (1 button, 1 hole, 1 flex..no other choices to mix up)
just check that you do need a whole new flex. sometimes it's a build up dirt/dust/skin/sweat that sticks the button down so it loses the bounce. other times it's just an over use..the prongs on the rear of the frame have flattened with wear. use a flathead screwdriver to gently lift to 45 degrees.
good luck.