Apply a Wordpress Theme i purchased to my existing site

Hi , i am planning to purchase a theme can you apply it to my site keeping all current functionality of Marketplace intact but changing the look to the new theme , Since in the current theme , user can open their own stores and sell . so we want to keep that , in the new theme , we merge functionality with current and be able to change the design , and add widgets to the page . please confirm , i prefer to finish it soon . This is project is to edit [login to view URL] it is a wordpress marketplace for FOREX and traders 1-make it similar to [login to view URL] 2- remove slider from old design , but keep all functionality for selling , creating stores , etc intact on current 3- we can keep New Items cluster of images from the old design in the new one as well 4- we do not need lot sof articles on the main page , so can be replaced with products , and we can keep one spot for blog entry and annoucements on home page of marketplace 5- we will need to categorize them as the widgets above FREE , Highly Rated