I have started studying for the 1級. I can't imagine I will pass it, but stranger things have happened. I did the same thing when I took the level 2; I took a trial run when I knew about half the necessary Kanji and vocabulary. The next year I passed it. This time is a little different. I have a better grasp on comprehension in general, my vocabulary is probably 5 times what it was then. It's easier to understand written passages, even if it is full of words I don't know.