i used to know how when i worked for iCella, i had to help one of the newbs make a new ebay store.
http://stores.ebay.com/wirelessmorebut i dont remember where to navigate to insert the code. you'd have to let me login to your account so i can refresh my memory, but basically there is a thing where you insert your own code and basically you just make a static page and make that your default homepage, and then add in a search box for good measure.
then for the pages that actually have content like
http://search.stores.ebay.com/wirelessmore...3227869QQsofpZ0 you just use their form. You can also trick out the css by looking at their stylesheet.
then for the item pages, you can do whatever you want for the content.
http://cgi.ebay.com/For-LG-Chocolate-8500-...1QQcmdZViewItem