New to Ubuntu

[Audrius]

Hello,

I've installed Ubuntu and I really like it. Unfortunetely I'm new to
Linux so several question have arised.

1. How do I install any application when I'm logged in as a user (not
root user, though I managed to create this account also)? For example
I need to install JRE so my browser (in this case Firefox) displays me
Applets. What steps should I perform to acomplish this? In fact I
installed this on my /usr/java directory when I was logged in as root.
Maybe there's some civilized way, like switching the users for
installation tasks or smth.

2. Suppose I installed JRE in /usr/java. Now I need to set-up my PATH
environment variable in order applications that uses java cnows where
to find it. How do I set up environment variables under Ubuntu?

3. How do I uninstall applications from Ubuntu? For example I want to
uninstall Gimp. What steps should I take?

4. What mp3 player could you guys recomend me. It would be great that
it's interface would be similiar to winamp. And it's also preferable
that the installation would be as friendly as possible :)

5. How to place my application's icon in the Applications "menu" (I
don't really know how it is called)?

Thanks in advance...
Audrius