i only know kinokuniya a klcc sells japanese books...
but there is an online site that may help you with your self-study: http://www.tanos.co.uk/jlpt/
however, do note that the site covers JLPT studies.

Level 3 you memorize dictionary can already.

Yes even though L3 was mean to bridge the gap between the previous L3 and L2, it's not really a hard test.

N3 is afterall, a bridge between the old level 2 & 3. It's definitely easier than N2. N3 won't be hard if you have studied the materials/syllabus thoroughly.

Take your time to read. It's more important to comprehend what you need to learn than memorizing the materials just to pass the test. (Assuming you intend to sit for the upcoming JLPT test in June/July)