I used the certificate I received on my wedding day - I never got any other cert????
Definitely photocopy it 10 times, get a JP or something to certify a couple. I did it all in one big hit too - I had to spend an hour waiting in line for the license change and new photo! Then drove to the bank, car insurance place was just up the road, etc... From memory Medicare was the hardest - government departments not knowing what they are doing! And Centrelink somehow had me entered twice and that was a pain to fix!!
Several of the companies allowed me to scan and email in the certificate - things like health insurance.
It wasn't that hard - and truthfully I was rather excited to tell everyone I was married!!
And YES - definitely practice your new signature before you hit the bank or Dept Transport!