OK,
Not a problem,
Pull the deck off
Pull off the nut holding the pulley on first
The spindle should now just push out towards the blade.
You might need to be a bit brutal but dont go overboard as you can break one of the mounting ears off the spindle housing.
the top bearing should pop out and the bottom one should stay on the spindle.
Once out check the spindle bearings for smoothness and the spindle housing mounts for possible cracks.
If all is well then buy a new spindle & blades.
If the bearings or housing are bad , buy a new housing complete ( part 25 on diagram ) as there is not much difference in price between a spindle + bearings and the whole shebang.
I usually leave the blade on as it makes a convienant handle but in your case I gather it is already off.
The stripped spline I presume is the 7 point star that the blade locks on to.
The dished washer & nut arre some times a separate part and some times come with the complete housing don't know why.
Just had to check because there are two different spindles used on that deck.
One has the 7 point star & the other has a mounting boss & 2 bolts to hold the blade on.