Magento Extension install conflicting with css and other errors

Hello, I need someone who is able to start right this minute. As marketing was to start 2 days ago for a promotion utilizing this free gift extension. I attempted to install this extension to my dev site [login to view URL] Dev site URL: [login to view URL] Live site URL(for comparison): [login to view URL] However after doing the install several issues have been noticed, 1. CSS conflicts on the category page, hovering products is showing a free gift pop-up behind the product image 2. CSS conflicts on product detail page top to bottom, see two sample links above to compare issues on dev with the proper styling on live 3. Adding product to the cart is now generating 404 errors, part of this extension is to automatically add product to the cart if the purchase qualifies. 4. Possible more css issues in checkout and cart, not sure due to the 404 pages more assistance needed if you are familiar with Bitnami and AWS Thanks