You appear to live in Japan which is a huge and i mean HUGE advantage. N3 is really just daily conversational. There are plenty of good books to help you for the test at Kinokuniya or amazon if you get those and do the drills you will pass. If you go outside and talk to people even watch dramas (which have daily conversation) that can also help your comprehension. BTW I am talking about physical books not websites, the physical books are your best test prep IMHO and they do include CDs for listening comprehension test. Also stepping outside. IMHO if you live in Japan N3 is an easy one (based on experience).