Vapors,
I am with Roman on #3.
As to #2 There is a reason that the current are 6V jars in series. It works better. They are probably in a series/parallel set to be 12V because 24v is unpopular outside of big thing and 42v hasn't caught on yet. Lead/acid batteries do not play well in parallel.
For #1 Without know which Cat engine it is, I can only venture a guess. There is usually a large cap with a T handle low on the engine. Unscrew
the T handle about a turn and it will be loose. If it is oily and nasty, that is the place. If you don't find that, look at the valve gear cover(s).
Matt