2
To update most modules just require that you copy the content of the new folder into the old folder, overwriting any existing files of the same name then going into admin and do an update. Usually, although not always, there is a 'readme', 'install' or 'upgrade' text file that explains what the particular module you're using requires. Here's the "normal" steps:
1) Close the site (prevents data from being changed by users during the upgrade).
2) Make a complete backup of the site (including database)
3) Copy the new files to the server
4) Update the module in admin
5) Verify the module preferences in case something was added/changed during the upgrade
6) Go to the front side of the site to make sure everything looks okay.
7) Turn site back on.
Typically I will also create/edit some test content, etc. while the site is closed to make sure all the features still work as expected before I turn it back on but you don't have to do this...