HI Kevin,

I also agree with what John said above. " depends on how you set up the .com."

In summary, there are no TLDs ( Top Level Domain .com. .org etc ) that Google finds preferential to others; they are all treated equally in rankings. There are some geo-specific TLDs ( Like yours ) that Google will default to a specific country and use that as an indicator that the website is more important in a specific geographic region. But all TLDs are treated equally.

Ref: http://googlewebmastercentral.blogspot.com.au/2015/07/googles-handling-of-new-top-level.html

If you think your ranking is due to .com? then you need have clear competitors analysis metrics before switching from .com to .com.au . But For sure it will have impact.

Hi Mark,

1. Yes, You have to do that in Previous website from where you want the redirection to happen.

2.  Anything whichever works best for you. But Fix one and work on it. check in google which version of your site is indexed more by "site:www.domain.com" and "site:domain.com" . Its easy to decide this way.

Note: Since its wordpress you can do it in the wordpress settings back end.

Related Thread here :

https://moz.com/community/q/changing-url-from-non-www-to-www