G'day gropperod, welcome to the forum.
1st good to see you taking interest in Dad's old banger.
The whole primary has to come off, so it's a good time to inspect all those bits as well. Have a look in the literature section for service sheets and manuals.
While your in there replace the seal behind the sprocket as well.
Sorry I'm a 1 finger typer so would take all night to give detail.
remove foot peg, rear brake lever, primary cover, primary chain, clutch, inner cover, Loosen sprocket nut, rear chain, sprocket nut.
Take your time, make lots of notes and or photos. If you get stuck ask again.
Cheers