Using Mac for the first time

[Rain]

I bought a MacBook yesterday, it's my first time using the system and I feel like I know nothing about everything. I only installed Adium (is there a better one?), and just trying things here and there with the system. Would appreciate some apps recommendations and maybe couple of FAQs that could help a Mac-noob.

I have couple of Qs as well. How do I install FireFox? I'm not sure if it's installed correctly, because when I add it to the dock and restarted my system, the dock icon was showing a question mark. When I clicked on it it told me that it will run FF through the .dmg file I downloaded. On the other hand, Adium is installed correctly because I could see it and launch it from the apps list. Second Q, I know that I can't re-download songs purchased from iTunes, but can't I e-mail Apple and tell them the situation (I lost my files due to a HDD corruption) so they may let me download them again? Because that would be quite depressing if they wouldn't agree :\

Thanks.

[T-Short]

App installations: Drag the app from the .dmg to the Applications folder. The Firefox .dmg (and many others) have an alias for the app folder right in the .dmg so you just have to drag it in there and authorize, done. Don't run anything from the .dmg, since it will unmount every time you log out.