Do I need an CMS for my website?
The decision to use a CMS for an website must be taken thinking of the following issues:

the type and amount of information will you display on the website

how often that information is updated

what ways to intreact with the website you'll give to the visitors
So, if your website will have to display large amounts of information, structured in sections, categories, etc, updated on a regular and frequent basis and you wish to get feedback from the visitors about the displayed content, then using a CMS is highly reccomended.

How difficult it is to learn how to use a CMS?
The objective of a CMS is to be easy to use for the non-proffesional, therefore everything about it is intuitive and user friendly. Usually the CMS will have in the administrative side a navigation similar to the one visible on the main site, and allow you do to the actions you need (usually add/edit/delete information, show/hide, sort lists and other similar tasks). The basic computer use skills are all you need in order to manage the content of your website using a CMS.

Are there any special requirements from the server hosting my website if I decide to use a CMS?
As simple as it may look, the CMS is a piece of software, so it has some special requirements. As far as the hosting server is concerned, it needs to provide support for a database server and the programming language the CMS is written in. Please note that your hosting account must be configured to:

support the database type and programming language needed by the
    CMS

provide at least 1 database where the CMS will store its data