A handbook of colloquial Japanese / Lists

You should read all these books (except for the dictionaries) once, without trying to memorize or learn anything. Some give info that the others don't give, but mostly they just teach in different ways and by the end of it you'll actually understand how Japanese works by the time you start to really learn.

Regarding the ones that are about the "written language", yes written Japanese has changed but books from 60+, 100+ years ago use that old language and people still use it today sometimes (in jokes or historical things, ex. anime set in the 1920's). it WILL appear if you move to Japan, you WILL need to know a little about it if you want to read classic japanese novels.

The spoken language hasn't in more than 100+ years, the only difference is that some of the words have been replaced (ex. there is a new word for "wallet" now). Some verbforms are "old" and modern books don't teach them, except they are still used every day in certain dialects of Japanese or otherwise appear in some fossilized words.