Sydney Connection Question

[Ben W]

Thinking of booking a flight on Qantas to OZ and back at Christmas. The return has me flying from MEL through SYD connecting on the DFW departure. Connection time is only about 90 minutes. I've never connected through SYD from a domestic before so wondering if there is a shuttle bus between the terminals and if 90 minutes is even enough time? Would I need to go back through security again through the front of the terminal or is there a bus like they used to have in the old Ansett days that would drop you in the terminal?

Thanks for any replies/ advice!

Cheers,

Ben