FJ1200 Fork Seals

I am confused with what my manual says about changing fork seals. Is this considered a full rebuilt and is this difficult to do? Also, should I do both or just the one that is leaking? I read somewhere that there are two ways of going about changing them. "Either remove the fork leg down through the yokes and replace the seal from the top or undo the Allen bolt at the bottom of the slider and remove the sliders from the stanchions." What are the pros and cons of both of these? Any replies would be appreciated.