hi and welcome to the forum! You will find a LOT of great advice and help here ..... and perhaps the odd smart A@#$e
Could you post a couple of pics of the wall in question? Reason I ask is that you allude to vertical boards and I am wondering what profile they are - this will help in determining removal method (though Cedar is notoriously brittle and soft). Can't help with where to get Cedar siding in Adelaide sorry, but surely someone will know on the forum - perhaps ask in one of the timber sections as well.
have fun and good luck!