I can't tell you how to get to the sprag clutch but if the problem was some broken gear teeth in the drive between the electric starter motor and the sprag clutch, removing the gears with the broken teeth would get you safely up and running.
You may have to remove the inner primary case to get to the gears but removing them should be just a matter of pulling them off or, at most, removing a circlip that restrains them and then pulling them out.
As I say, if the sprag clutch is okay, there is no reason to remove it so you won't have to remove the drive sprocket, clutch, primary drive chain etc.
If you don't remove the gears with the broken teeth, they will eventually lock up