You have to remove the bellhousing to do the front seal. Make sure to orient the seal the right way. You're installing it from the inside, so it goes with the open end and spring towards the trans. Also, make sure to have a clean mating surface and use a good sealer.
On the rear, the big yoke nut can sometimes be tough to remove, other times it practically falls off. Be gentle prying out the old seal, and you need a long socket or the factory tool to properly install the new seal, around the output shaft. Check the "ball" on the output shaft to make sure it's round, not pounded or worn unevenly.