There is a cover/retainer containing the seal, retained by four bolts. There is then a cage that also needs to be pulled that contains the bearing. Take the transmission top cover off, support the mainshaft from dropping, and extract the cage - I think it has 3/8 NC forcing screw holes in it. Use your retainer bolts in those forcing screw holes to push the cage out. It will mess up your gasket so go ahead and order a new one, bearing, and seal since you'll be looking at them anyway. Your other option is to slip a speedi-sleeve on to the shaft in-situ.

You don't need to remove the back plate - just the front cover that includes the shifter. Easier the seat removed but not required I think

Yes you're right about disconnecting the steering clutch levers - my bad, I forgot about that. Still, not a big chore - six bolts, then the split pins to enable you to undo the adjustment nuts. Make a note of where they were (take a close-up photo with a ruler is one way) so you can put them back there to get an initial setting when you reassemble