Difficult?, no, a lot of work, Yes. If you do not have to repair the part, just paint, it is not worth the work. Especially since you are not changing the color. Any competent paint shop should be capable of prepping and painting the part on the car. Do not forget when reinstalling it there is always the chance of damage so consider that too. If you had to do other work (like cleaning or replacing the radiator) then removing the part should be considered. All of the front painted parts get "Road Rash". Try Dr Color Chip (Drcolorchip.com). That might be all you need. Once you get good at it you can get some amazing results.
David Teitelbaum