Can I change this seal with out taking the axle apart?

 

no u can drop the drive shaft u will see this nut its torqued to 240 0r 220 have to double check but make sherr u do it right the part is like 15$ if u dont do it right this is what will happen

 

So impact gun to get the nut off. Do I have to replace the crush spacer (don't know if that's the correct term) when I replace the pinion seal?

 

Heres what I do with pinion seals and never had an issue.
Mark the bolt and the center of the pinion gear with a chisel
Remove the bolt and yolk
Remove the old seal
Put black rtv on the edge of the new seal
Take a large socket, or piece of old pipe to seat the new seal
Put Black rtv on the splines of the pinion gear, a decent amount
Put the yolk back on
tighten the bolt until the marks made with the chisel line up
Re-install driveshaft.
You shouldn't have any crush washer issues as long as you don't over tighten the center nut.