That is a far bigger job than you anticipate.
Painting will be extremely difficult to achieve a good match - most bodyshops would try to blow-in across more than the wing to minimise the difference.
There are 2 main methods employed for dent removal;
1. Applying pressure from behind the dent (pushing/levering)
2. Applying pressure on the surface of the dent (pulling)
Method 1 isn't really feasible due to space issues as the wing gets closer to the headlight - the area behind the wing will drastically reduce - wings aren't always hollow either - there can sometimes be some strengthening behind.
Method 2 is the only real way to repair the wing whilst it is fitted onto the car - you would need to use a substantial slide hammer, and be prepared to drill self-tapping screws over the area to be repaired - naturally, this will only go so far, then filler & paint will be needed.
If you are looking at replacing the wing - the bumper & headlight will need removal also.
Personally speaking, I would push the bodyshop further, this really is beyond the scope of a roadside repair (if you want a good result).