I have the tell tale sign of a leaky rear main seal (motor bell housing area has oil on it)

The PO said that he replaced the stock clutch with a HD replacement but I notice that with a loaded trailer that the clutch has a grabby feeling in first (I can usually make this go away if I work the clutch just right)

So.... how hard is it to replace the rear main? Any special tools required? My thought would be that I would do it at the same time that I replaced the clutch but dont want to have any unexpected problems.

 

Ttt.....