A note on baka... from my understanding, it depends on where in Japan you are as to how insulting it is. For example, it is more of an insult to say baka in the Kansai region versus the Tokyo (or Kantou) region. If you're in Tokyo, it's more of an insult to say "aho" than "baka".
But just like you would in English, it's best not to call people you are not familiar with stupid. Thankfully, guns are illegal there. You could get shot calling the wrong person stupid here. XD
There is a book called "Making Out In Japanese". It goes over really well on the various degrees on slang and when, where, and who to use what or not to use with bad language. I personally like to know what the bad stuff is, so that I can understand if anyone starts to insult me or whatnot. And also so I can better understand the culture. I found it helpful when I studied German as well, because I understood when I was being insulted (which, when I went on my exchange there 10 years ago, I was called a pig... which is a major insult in German, more than it is here -- we're most likely to use sexual innuendos to insult people than by calling them animal names).
... :) Good luck! Maybe we can talk together sometime. I've only been studying Japanese for the past few years, but off and on. :) It's fun to find others who enjoy studying it.