THESE PANELS ARE MADE FOR THE GENUINE GM EXPORT MARKET
(IE) MIDDLE EAST UK AND US MARKETS SO REST ASSURED ALTHOUGH THESE PANELS
MAY NOT BE MADE IN AUSTRALIA,THE FIT AND FINISH OF THESE PANELS IS PERFECT! The only difference is the cost!
Panel beating/painting is expensive and not really for most DIYers, even experienced ones. The tools are expensive (relatively speaking for something you won't do often) and it requires skill and a fairly clean environment, using 2k paint in residential areas and without filters or a booth can be an issue etc....
As for panel beaters, if they charge anything like mechanics, you'll be paying them about $100 an hour to take the time and beat the panel straight, bog it, sand it, then paint it. They will usually have to paint the car around the panel as well as the panel to get the colour to match depending on the type of paint (particularly if it's metallic). Black is probably one of the easier colours to match. The colour may or may not match as much on an off the shelf painted part (if they exist) or wrecker panel (usually they're pretty close though), but it is substantially cheaper and faster - also factor in the amount of time the car might be at the panel beater vs. just replacing the panel in a few hours.
I have a feeling the panel in this example is second hand as you usually can't buy painted ones, so highly likely it is genuine.
Largely, in the end it depends on how the damage was caused, if it was an accident, how the car is insured and if it's cheaper than the excess, if you bought the car with existing damage etc....