Re: clutch shaft bearing "is it important ?"
I punched out and replaced my clutch shaft bearing only after experiencing big problems. It was impossible to keep the clutch adjusted and the chain was rubbing against the drive sprocket cover.
If your shaft bearing is bad, you will be able to wiggle the drive sprocket a bit.
I hope the bearing that fell out of your bike was only the actuator ball in the end of the clutch shaft. It's much easier to replace.
“You're only young once, but you can be immature as long as you like" -Unknown