relatively easy.
remove driveshaft. use sturdy THIN tipped straight screwdriver to tap edge of seal around the lip and transmission tail shaft housing until the seal parts enough to use a standard tip screwdriver to finish tapping the seal out.
clean seal mating surface inside tail shaft housing.
then use the CORRECT seal driver, or make one from PVC pipe parts that fits the seal lip entirely, then tap in new seal.
you may, or may not, want to coat the outside diameter of the seal with your sealer of choice.
however, you MUST use a nice coating of wheel bearing grease on, and into the garter spring showing on the back side of the seal.
this will prevent the spring from falling out of it's retainer groove when it is being installed.
lightly lube up driveshaft yolk on the outside, and reinstall. done.
hope this helps in some way.
perhaps others may chime in with more tips.