Integrate WordPress Blog with existing site?

Hi,

I have an existing website and I’d like to integrate a blog into my site. What would I need to do to embed a blog into my site? My site has an existing header and footer and I’d like the blog to appear in the middle.

1. Do I need to know PHP to integrate the blog into my site? I know HTML, CSS, and Javascript, but not PHP.

2. Since I have my own design already do I need to start with a theme? My goal is to leverage my existing header and footer and “plug” the blog in the middle

3. I’d like to add a sidebar with Twitter updates how is this done? Is custom coding required?

4. Can I post videos?

Sorry for the newbie questions, I’m totally new to blogging and I’ve been tasked with getting things going. Any help appreciated.