1. You will need to change character encoding to japanese,
this topic tells you how to do it. Also you will need to meet the minimum PC requirements.
2. 1280yen/month + 100yen/month for every extra character you create. You pay with creditcard.
3. On ragnarok (where i am), there is a linkshell called NeoGundan, as far as i know, everyone speaks english there.
4. I dont think so...