All things blogs
Once you submit your blog to Google, you are not supposed to resubmit it and you can just update your sitemap. You can install the sitemap plugin if you are using a blog such as Wordpress, which automatically keeps your sitemap up to date. These sitemap plugins also reports Google that your site has changed. You can also use blogging software for the generation of sitemaps. However, if you are not using this software then you can create sitemap on your own with the help of tools offered by Google for creating sitemaps.