You should be able to pop the old seal out.Put the new seal in the freezer for awhile,grease the outer & inner edges, then put the new seal in. I done this a few times on Shovels & Evo's.
tourbox
I think I left this part out
The primary is off the bike. If the primary is on maybe it wont be leaking?
I am waiting for gears and a new clutch basket so the bike is parked with the primary open and the primary and clutch off the bike leaning on its jiffy stand
If the primary is off, why not go ahead and replace the starter and mainshaft seals in the primary? If the tranny seal is toast, you can bet that the ones in the primary are not far behind...