Turning into a shipgirl from human happens in some works, but not very many official works. Or at least the official ones where it might have happened aren't clear on some things.
As for the gender swap thing, only ever in some fan material to my knowledge. And even then rarely.
Well it's more so there's a lot of official works, and the most core of those works have barely anything to work with(the game) or are just a mess(the anime.) The rest of the materials(manga, novels, side games, table top RPG...) are for the most part in their own continuities, contradictory, or something along those lines.
Really kancolle is one of those things where the fan works are just better to go through once you have a good enough idea. Doesn't hurt that some of those fan works are better than a lot of the official stuff.