It's no where near as hard as everyone makes out...
You can't buy the cable by itself, so what you have to do is buy a whole new window winder regulator from ford for $77.
Then, take your door trim off.
Wind the window down (or push it down if the cable has completely broken) until you can see the 2 bolts that hold the bottom of the glass onto the track. Unbolt these.
Slide the glass out of the side channels (it may take a bit of fiddling around, but it WILL come out!).
Remove the existing regulator. If it has been changed previously, then it will be bolted on. There are four bolts on the runner that the glass slides on (2 at top, 2 at bottom), as well as 3 bolts on the winder mechanism (the part that the winder handle attaches to). Otherwise, it will be held in place by rivets, simply drill these out and replace them with bolts once you have installed the new regulator.
Manouvre the old regulator out of the door (again, it will take some fiddling, but will eventually come out).
Manouvre the new regulator into position and bolt it in place at the same 5 points as listed previously.
Position the glass and bolt it on.
Re-attach the door trim.
I'm doing this from memory, so forgive me if it's not 100% accurate. Hope it helps.