Replacement of the clutch on your Focus is only feasible when the whole sub frame is removed, to gain access. As such, this is not a D.I.Y. job and even if you DO attempt it, the chances are that the sub frame bolts on your year/model, will snap, in the process, making the task much more involved. Best leave to a main agent or a reputable garage that has the tools to hand, just in case it goes wrong.
M.E.Chanic
November 2010