Editing the home page (Front Page) will depend on what you are looking to change? Right now it's setup as the default WordPress blog "home" page which is where your blog posts would show. When you say a promotional slideshow widget to the side, are you referring to the right sidebar?
As for the Pro version, if you later decide to opt in for that one, you would simply go to my site and the theme's introduction page, click on the button to purchase it. Or, you can do the theme membership which is access to all themes. You would get more widget positions, a portfolio function, more typography and page elements, couple blog layouts, more theme tutorials, and more support tools.
For your other question....you could add your own social media links to the top black bar, but you will need to do a small modification to the header.php file. Depending on what you would use, referring to the plugin's documentation on how to integrate it into a theme should help too.