Help!!!! 3.9v8 crank oil seal

Hi all I have a 3.9 v8 mated to a lt95 gearbox. After off roading on Sunday I have developed a oil leak from the bell housing where it mates to the engine. It is making the clutch slip! I think it may be the crank oil seal! I will pull the engine and replace the clutch at the same time. How hard is it to replace the crank oil seal?? Also what clutch kit do I need I want to replace the friction plate thrust bearing and pressure plate.
Many thanks Dave

not sure on most of it, but all the clutch kits I have come accross all have friction plate, bearing and pressure/cover plate in them