How do I set up Apple's Messages app to send and receive my Google Voice texts? Can this even be done?
As far as I am aware this cannot be done. Google appears to not even being further developing Google Voice like they did when it first came out.
You should use google voice's app for that
App Store - Google Voice
I think he meant Apple's Messages app for Mac. I would also like to integrate the two.
In the meantime, though, there's Growl Voice. Allows you to text/call using your Google Voice number, and lives in the menubar. Very convenient since we can't (as far as I know) use Google Voice with the native Messages app.