This is the steps when I did mine.
1. Empty engine oil.
2. Take left footpeg off.
3. Take clutch cable off.
4. Take off gear shifter peg.
5. Undo all bolts retaining left side cover. Keep the bolts in correct order and placement.
6. Use a large screw driver and piece of wood to pry off cover using the two tabs on the cover... one is located near the clutch cable adjustment bolt, the other on the lower right side when looking straight at the cover.
7. Use a piece of wood and rag to wedge between the primary drive sprocket and clutch teeths to stop them both from spinning. Be careful not to break any teeth!!!
8. Undo the primary drive sprocket bolt (mine was anticlockwise to undo... the newer models are clockwise I believe).
9. Undo the clutch retaining bolt (mine was anticlockwise to undo). The bolt may be hidden if grease has made the washer stick to the top of the clutch hole... just use your finger to pull it off!!!
10. Undo and remove the primary chain tensioner from the bottom of engine.
11. Pull both primary drive sprocket and clutch off together with the primary chain... they slide out easily and smoothly.
12. You can now remove the sprag clutch from the primary drive sprocket... or if you had bought the whole primary drive and sprag assembly, just replace the whole primary drive sprocket with the sprag already in it.
Reassemble in reverse order of above.... just make sure you put plenty of locktite on primary drive retaining bolt!!! I used blue locktite. I also used a new side cover gasket and grease...the factory only used gasket maker sealant.
One tip, there is a dowl like metal thing with protruding semi circle thing, make sure you turn the semi circle so the cover can go back on... the dowel thing is actually the axle for the starter motor gears!!!
Simple really.... hope it helps.... sorry for my less than technical nouns used.