Svn 1.4 - mp3 support and changing the installation director

Hi ALL!!
This is my first time with asterisk and my first post:)
Please be so kind and give me few clues for the good beginning:)

I am using version 1.4 from svn.

I have three question:

  1. In many docs on the web there is an info to make asterisk by invoking #make mpg123 in order to have the mp3 support, when I try to do it this way make informs that there are no such make rules.

  2. I would like to have my all asterisk stuff (asterisk,addons,core-sounds) installed in the asterisk system user home directory.
    Is it sufficient to set the INSTALL_PREFIX= in the make file to the desired value??

  3. is it possible to get a packet of core-sounds directly from the svn?

Thanks in advance