It would be from NSW transport. You'd have to mail them the plates and they'll mail you out a cheque for the remaining rego.
You'd need to do a transfer of ownership. Shouldn't be difficult to do, just download the forms of the Queensland transport website before you head down so that if you need to get the old owner to sign them, you can.
Insurance. Just ring them up on the day and take out a policy on the vehicle. You get a cooling off period (either 14 or 28 days, I can't remember) where you can cancel it before having to pay any money (unless you crash it in that time, then naturally they'll expect you to pay up) (Used to be that you'd get a cover letter for a short period, but I'm not sure if insurance companies do that any more, Just car's didn't for me)
Have you looked around up here for a R34 first though? I know that there have been plenty for sale over the past year.