Hello and welcome to Just Answer!
Once you have the driveshaft off, you need to mark the pinion shaft and the nut in a straight line with a cut off wheel or chisel. You need to mark this so you get it back on in the same place. Once you have the nut and pinion shaft marked so you know where the nut is, you can remove the pinion nut with an impact and remove the yoke. Sometimes you have to use a two jaw puller to pull the yoke off if it's tight. You can tap it off with a hammer as long as you don't use excessive force.
Now you are ready to pull the seal out and replace it. Inspect the yoke where the seal rides for excessive wear and if the yoke surface is grooved, you will need to add a speedi sleeve to the yoke so the seal can ride on a new surface. If the yoke was good, put the yoke back on by tapping it far enough so you can get the washer and nut on. Then clean the threads with a brake cleaner and install some red loctite on the pinion threads and install the nut till it gets tight and then tighten more to align your marks. You can go the width of a cut odd wheel tighter if you want.
I hope this helps, let me know!