While having duplicate content and urls is common with ecommerce sites it is fairly easy to fix.
For your content vs other sites if you are selling products sold by other retailers you need to go to the trouble of rewriting the content vs just copying and pasting it from the wholesaler. Adding reviews, additional images, and videos helps as well.
To make sure the multiple paths to your pages does not end up with you having the same pages getting counted as multiple let Google know which ones you want to index by using cannoicals and making sure your site map only includes the pages you want to index.
It does take some work but it is not really that hard.