Depends a little on the mileage this machine has. A little on whether this is hard or easy miles, judgement call. And whether you want to do the rear seal just because you are the get it out of the way now kind of guy.
I recommend that you pull the trans out to do just the spline lube. Use Honda Moly 60, available at Honda dealers but they usually have to order it, or on line. You will be also greasing the rear wheel bearings and the swing arm bearings so you need wheel bearing grease, get the tub of grease that looks like a colorful margarine tub. You also need the gasket for between the swing arm and Final Drive, that's cheap. And before you take it apart look at the drive shaft boot and it's two clamps. If the boot is cracked replace and the clamps should be in good order.
The spline lube grease goes only on the male splines of the transmission input shaft. DO NOT put grease on the female splines of the clutch disk. You have been warned.
Also grease the splines of the rear wheel and away you go.