Customize Magento Checkout Page

We have just installed a new one page checkout extension which is working perfectly, but requires some layout / design changes. Please see the attached screenshots for reference. Image 2 (checkout2) refers to the final stage of checkout before finalizing the order. This section should be no more than completing the order but as you can see there is too much information displayed and the colour scheme is incorrect. There will be additional work if the task is carried out efficiently.