customizing oscommerce to use our template

we need to make the shopping cart look like our site (same template) not just the colors and theme but the size of the tables, the bottom the top and the sides. To be more specific i dont want the customers to see or know that they are in a different site. if the customer add something to the cart, the cart should show that it has 1 item, etc. then when the customer decide to see the cart or check out, to go to the html that we created and if it decide to check out, then fill the info, and then after submiting the info go to another page where we have thank you for your order etc. please visit toyrrific . com and look for yourself. I will provide images, html templates, etc.