install or upgrade newer or older gcc version
 

I have gcc version 4.0.2, and I need gcc version 3 to compile some software.

Here's where I'm not sure what to do - should I downgrade, or should I install a new gcc and run it separately?

For the former, how do I change gcc versions? I see a lot of guides that point to: Installing GCC - GNU Project - Free Software Foundation (FSF)
which only tells u how to do new installations

As for the latter, how do you deal with 2 versions of gcc? how do u specify one version over another?

Thx in advance
and oh yea if u can, plz go into as much detail as possible. I'm finding it difficult to find guides on the web for simple operations in Linux like upgrading gcc, etc.

since gcc is a core part of your operating system don't try to upgrade/downgrade your core gcc. When you need another version of gcc
just use the version you have to compile the new one and install in a safe place like /opt/gcc3.

use these instructions and follow them to the letter for a working version of gcc 3.3.6
http://www.linuxfromscratch.org/blfs...eral/gcc3.html

to use your gcc3 like the instructions say you can use these shell variables
export CC=/opt/gcc-3.3.6/bin/gcc
or adjust the PATH variable to start with /opt/gcc-3.3.6/bin
with something like
export PATH=/opt/gcc-3.3.6/bin:"${PATH}"