Help with language please! Any help i much appreciated

Hello, everyone!
I am in a bit of struggle to change the language on my site, (which I decided to let WordPress power), and I would really appreciate your help!
So here is the story:
I have a hosting over at bluehost, and I decided to install wordpress on my domain. So far so good, but I really need to change its language. So I went to the ‘WordPress in my language page’ and followed the instructions, but to no avail. I edited wp-config.php and I uploaded the .mo file correctly, but there was just no effect. I am running a theme called iFeature. I really don’t want to change it, because I have already spent a vast ammount of time customizing it and setting up everything.
Same thing with my sub domain, but this time with a different language! I can’t get French, German, Greek, Bulgarian, Japanese, or any language running.
Any help on what I am doing wrong?
Thanks a bunch in advance and I really hope you know a solution.

PS: I also have a second question, and I will try to ask it here instead of posting again: I want to make my subdomain an exact copy of my main domain, but in a different language. Any tools/walthroughs to help me with that? Or does it suffice to just copy/paste the directories and files?

Thanks a lot in advance!