Help with a shopify website.

We have just set up a Shopify website and i am wondering whether you can change the look of the website but keep the theme? We need things like the menu changing, sub categories added, some banners removed, a meet the team and blog page added across the top etc. Either someone to do this or to give detailed instructions on how i can do this myself.
Budget is negotiable based on how much work it will take.
Price is negotiable as there is a few jobs that need doing.