According to my book for engines up to number #8S66782 its a 39 hour job and for engines number #8S66783 and up its a 10 hour job, hope you have the later engine as the transmission and flywheel has to be removed to get to this
That's because there isn't a very simple answer. That's generally a pretty major job.
You will need a repair manual: http://bit.ly/mitchell_repair_manuals_online
But you may benefit from seeking assistance from a professional.