Good for you for getting up the courage to do such a thing! Most people are content to sit in their rooms and watch anime or something, but you're taking the bull by its horns and that's really commendable!
As for advice, how's your Japanese? Someone else posted some good links on another thread for survival Japanese phrases if you are lacking, I'm sure they'll pop in with the same links again, hopefully. The average Japanese person you'll see on the street will usually be pretty scared of English and hence avoid you if you seem to be headed that way. There's various reasons but they're very rarely malicious, and actually for every one of them, there's one or two people who have taken an active interest in learning English and will jump at the chance to talk with you and help you out, maybe even show you around!
I find that you'll have no problem getting around, getting help, and having a fantastic time. English is EVERYWHERE, so you can even navigate the subways and train lines relatively problem-free!
I would say just bring lots of cash and get it changed out at the airport; hardly any place will take credit so never rely on it.
If I can think of anything else I'll post it! I hope you enjoy Osaka, that's my city!
