Webstore doesn't replace your current eBay store design, instead it will create a storefront for your eBay listings outside of eBay.
But if you are looking for a solution that will design your eBay store, you can do that with our Store Designer solution.
With Store Designer you can design your eBay store with one of our design templates and also customize the design just like with webstore.
You can watch here how it works:
Let me know if you have any other questions, or if you need any help setting up your new store design.