Wordpress devlopment and customization

Our current website is www.usabuttons.com. It is a wordpress website with a custom built os commerce back end for our ecommerce. I wish to keep the oscommerce ecommerce part exactly as it is because the shipping methods were custom coded for us. We use links to the shopping cart from the wordpress pages and that works well for us. The wordpress site I want changed to using the Avada theme(it is responsive), but keep our current clean website look/feel. We are open to improvements in the the look, but at this time we are not really looking to add features. In addition, we have additional content(video and new logos) and graphics that we would like to incorporate into our product pages. Hope this is more clear. ----------------------------------------------------------------------------------------------------------- There is absolutely no common data shared between the Wordpress and Os commerce. They are entirely independent. Our wordpress pades website just uses links to the shopping cart from the wordpress pages. I do not want the oscommerce shopping cart redesigned. I understand it is not responsive and does not look like the rest of the website, but I had spent a very long time implementing the code to calculate our complex shipping requirements and wish to keep it like it is until we decide to move to a new shopping cart(probably next year).