installing new programs

I am installing the newer version of a few programs
and I have few questions regarding it.

When I install the new program will the newer
version simply be installed over the older version, or
will I have two copies of the program? What would be
the "proper" way to do this. Should the older version
be removed first?

When I am doing the install I have the directory
with all the files in it. Can this directory be
deleted once the install is complete?

What is the "proper" way to uninstall a program. Is
there a script that does it, or is it safe to just
delete files or directories?

If it makes a differnce with these question, I am
running Slackware 8.1 and a new version of Debian.

Any help regarding these questions would be greatly
appreciated.

                              mike

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