Oft said here.... Get the shop manual for your truck... Short of that, check out the "old Car Manual Project" Search in google. It will have the pages you need.

Basically, remove driveshaft, remove yoke, pull seal (carefully), replace. I've heard the torque requirements to remove the yoke nut can be quite high (200 or more ft-lbs).

Good luck! Enjoy the process, that's most of the fun.

Current fleet (subject to change w/o notice)
\'49 GMC 3/4-Ton , 60 Austin Healey Frog-eye Sprite (some assembly required), 2011 Dodge Avenger, 2015 Jeep Cherokee. No, they don't all run.
My other ride is a (B737)no, (B767)no, A320.... Update... was Embraer E190, now Boeing B787.

Knowledge is a wonderful thing, but ignorance means you don't know you can't do something.