Customize Shopify Theme

Hello, I will be working on setting up a Shopify store but I want to modify the Brooklyn Theme (Free Shopify Theme). I want to change the cart icon to a bag icon. Moreover, on the product page, I want the products images displays as thumbnails on the left side of the main photo, and also, when the user hovers over the product image, it zooms in the image. Images attached to know what I want.