Alternate Post Template

Hi everyone, I am relatively new to the WordPress Scene, been working with it for about a year now and learning with every project.

I have come across the need to have a menu attached to the first post in my ‘news’ page which i display at /category/news

This menu should only be attached to the first post. I have a template for each post entry defined within post.php but since this repeats for every post, i cannot include my menu within post.php.

I have found how to create alternate ‘styles’ for posts, but these posts require a more complex template structure than a simple css class can provide.

I need to include the menu in the post.php template so that the post expands to match the height of the menu regardless of the content of the post.

The only way I can figure to do this is if I could define a post-1.php for my first post, include the menu here, and then have a post.php for all the other posts in the list.

Is anything like this possible?