MarketPress - customization pages, css, design

Hello, I installed the first time the plugin and everything works fine, but the problem is that some things need to change the design shown. It now appears that I am using the same wordpress templates provided to create pages. I want to do a different interface, and if I now change the css, changed my blog.
Can you help me solve this problem?

Product description page.
When I want to see more product information, I click on the image or on the button for more information and this leads me to a page that has the same structure as my blog, and if I make changes to the css, I also changed my Blog. I need to separate the page associated with this blog to my own design. How I can do?

Submenus in main menu.
I do not want on top of my web menu buttons have no submenus. How do I remove it?

Sidebar at Checkout.
When I do a test checkout, and start on that page, I see that you see a sidebar with all pages and categories in my wordpress. How I can remove this?

Button>> more info.
In the list of products next image is a description with a button for more information, I would like to separate one or two lines below the text. How I can do?