Plugin for post content/meta data?

Let’s say every week I post about five different topics, and all of them contain an image and some basic info at the top (content). Each topic is unique and has its own meta data. The content that follows this initial info varies week to week.

Is there a plugin that would allow me to store the information that I use weekly, then select it from a drop-down list (or use a shortcode, but I honestly don’t even know what that is exactly or how to use it). I just copy and paste the same HTML over and over… seems like surely there’s something better.

I tried the Single Post Template and Custom Post Template plugins. I tried posting my HTML in various places within the single.php file. I was successful in getting the custom template to appear in the drop-down menu, but the templates I made did bad things, like move my sidebar to the bottom. I’m thinking that sort of thing is meant for the style of your posts and not the actual content.

Any advice?