To replace the gearbox output seal you will need the correct flange removal tool.
Don’t be tempted to try and lever or press it off against the alloy casing.
The seals currently available seem to be of poor quality,I’ve reverted to using earlier mono/twin shock ones.
Also be aware,on a para,a small amount of sealant should be used at 12oclock on the seal/housing as there is a small notch out of the casing to allow the swing arm to vent on earlier mono/twin shock bikes.
The bevel input pinion seal also requires a special tool to undo the “castle “ nut into which the seal fits.
It’s a good idea to also replace the compression ring which the seal lip runs on as these wear and/or can corrode.
Hope this helps but without the correct tools you are going to struggle.