I was told that all distros (or most) come with "Sendmail"

I was told that the main thing to get started is to make sure that you have the most recent version of "sendmail" which according to their URL is 8.13.0.

Should I follow these instructions: install help

or since I already have this installed on Fedora Core 2, should I somehow do a upgrade?
I am not even sure what version I have but I must get rid of my Exchange Server since I am leaving the company and my license key for Exchange expires.

So I guess I don't know if I should still install the new version on top of the old or if there is a proper way to upgrade...or even if I have the most recent version.

Thanks for any help on getting mail set up on my server.