I need advice…please help..

I owned HTML5 kindergarten website. It's static website.
The website designed in Dreamweaver CS3 from HTML5 template.

I would like to make it dynamic (content management), I mean that I could add pages, images, videos from some interface/platform (something like WIX concept)

Do I need to hire some web developer what will develop this kind of platform to make this website or I can use editors like ckeditor.

In the bottom line I want when the kindergarten teacher enter the website, she will see two fields: username and password. After login she could see kind of control panel with pages names of the website. She could get in update the content of the pages and add new pages + images to the website. In the end of each update she will save the changes by pressing "save" button.

I know you probably think that the perfect solution for this is to wordpress or joomla…. but I need to build my unique platform.

1. I don't know what I need for this: Sever Side - Data Base solution? PHP developing?
2. Who do I need to hire?
3. Do I need to hire PHP developer for this? How much this could cost?
4. Is it difficult or maybe I can use some free solutions for this (some converter from static to dynamic, I don't know)
5. If I want to make it by my self, what do I need to learn to develop this kind of platform by my self?

I will be thankful and appreciate each answer of you.

It is important to me to develop my own platform or to use some relevant tools to make my platform unique. It will serve my all kindergartens websites.