If you ever want to replace those dash panels, I found this place
that sells them.
ACC-1 and ACC-2 are simply for whatever accessories you want to have on switches. SP has a good answer for a heater equipped boat, mine aren't hooked up to anything (but will be eventually).
I don't know where to get those little pieces; you might have to look around places like this
to find them.
I don't know about the cigarette lighter; mines missing also.