Your 'colour' will always be out of stock, you might be unlucky in finding something that looks close...
I have a nagging memory that
Yes, you will need a special plastic 'primer'.
Sounds like they are quoting to re-spray the bumper, probably the best solution - spot repairs seldom work on metallic paint due to the way the paint / metallic particles need to flow in the correct direction to each other, never mind the issues of old paint and new...
Everyone says that when they don't want to spend money on the correct / proper repair and want a bodge, do it wrong and your repair could be far more noticeable than the original damage!