If you are planning a visit to Japan, short or long term, and intend to drive, then yes you will need an international driving permit. Even if you don't plan to, if you just want to be able to drive should the chance arise, you will need it and the low cost versus the convenience means it's worth getting.
This guide to setting up an apartment in Japan can help you save time and money. Not everything you take for granted back home is available here but on the flip side, there are other conveniences only available here. Tips for ALT's new to Japan or for anyone moving into their first apartment in Japan.
If you are coming to Japan as an ALT then you will need an apartment. Luckily most ALT's will have assistance finding an apartment or won't even have to give it a second thought as either the company you are coming with will organize it for you or the board of education will have an apartment for you.
If you aren't in this group and have to organize an apartment yourself then here are some tips and information to help you know what to expect.