@kyl,
I know this is an older thread, but I have the answer for you. Delta's refurbished plane is only the interior. New seats, lighting, etc. It has nothing to do with mechanical aspects. If your talking about a long haul Australian flight, that is likely the 777. They reconfiguring the awful herribone seats in Delta One, replacing them with the suites. They are also adding a new type of class (in between Delta One and Comfort+) called Delta Premium Select . I'd call it a business class type of seat, similar to a first class domestic.
For Comfort Plus there wasn't much changed. You will have designated overhead bin space, early boarding, and 3" more of leg room compared to Main Cabin. It will be the 3/3/3 cabin configuration. Personally, I like the window so I can lean against it when sleeping. YMMV.
You can easily find videos, pictures, and reviews by googling Delta Refurbished 777.
I have been on the refurbished 777 in Delta One and found it lovely. In fact, I preferred it over the Airbus 350.