wordpress site & plug in help/setup

I need a wordpress e-commerce site. Must be easy to edit (layout, design, widgets etc) especially on the home page. Would like to have a slider at the top, widgets on the right hand side and below the slider. Can be something like this [login to view URL] We can even use that theme and modify it if we have to. I need an e-commerce solution/shopping cart that's compatable. - I know these can be free plug ins or purchased. I also need to have 'main' categories and then sub categories of products. For example I want to have 4 or 6 linkable images on the main page such as- : residential, commercial, marine, outdoor, etc that once clicked they would go into those categories with the respected products that go in there. I will need help tying the shopping cart plug in as well as the api for the merchant processing and SSL.