We're just about to the point in our kitchen remodel where we're putting in the lighting. We will have 8 canned lights, three pendants over the island, a recessed light over the sink, under-cabinet xenons and rope lights above-cabinet. I'm wanting to put in some sort of single switch plate that I've seen where there is a dimmer and multiple buttons that will select the section of lights to be dimmed. Are these incredibly expensive/difficult to install? Is there some sort of computer that is required or does the single box contain everything that I'd need?

Yes they do make a single switch plate with multiple buttons and a dimmer. <a style="text-decoration: none; color: black;" href="http://www.westsidewholesale.com/">Lutron Dimmer</a>
and wall plate from the Grafik Eye Series may be the best for this purpose. It can be a more expensive option. It is harder to use, looks nicer and takes a professional to install. The system can be used with or without a computer. <a style="text-decoration: none; color: black;" href="http://www.westsidewholesale.com/">Leviton Dimmers</a> can be a less expensive and easier to install option the model to look at is the Leviton X-10 series.