Change a Dahua lens from 2.8mm to 4, 6, 8, or 12mm?

should be easy enuf. I've swapped lenses in various Hik's & Dahua over the years. Just make sure to get the right size lens. the 5442 has larger sensor, but i dunno what size lens it uses (if it's the usual M12 board lens or somethign else)
Also consider that for the fixed lenses, the IR's are selected to cover the lens Field of View, so going to a longer lens (narrower FoV), the IR distribution will be wider and less focused on your FOV... May not be an issue if you're never using IR (staying in color), but worth considering...