Plenty of people eat raw fish without marinating them in acid, notably the japanese and to a certain extent all western countries where sushi has become widely popular. Personally, I think most raw fish tastes way too bland or simply unappetizing without marinating it in lemon juice first.
About the internal organs, I suggest removing all of them except the eyes, or simply taste for yourself and see what tastes good and what doesn't. A warning though, most internal organs will taste horribly bitter. And you are likely to find very small, barely visible, live intestinal parasites as well. The eyes can be really tasty once you get over the initial shock of the fact that they seem to be staring at you while you poke them out with a fork, and once you learn hot to prevent squirting eye fluid all over the place in the process.
About cleaning the fish, water alone is used, if you want. I usually do this to partially remove any potential chemical that may be used to keep them fresh, and to remove the bitter taste from the insides if I punctured some internal organ in the butchering process, which I always seem to do.