can’t upgrade wordpress or install plugins, it seems to “think” it’s still on a local installation

Go to ur wp databse and seethe table wp_options there u will see site_url in id 1 change that link to your site link. if its the problem you will solve it otherwise there is something else
-other idea to check where its causing problem or not is login to your wp-admin and check general under setting menu you will see the site url from there :). enjoy if this is you problem