Looking for a simple automation to replace a smart object in a mock up

[Susanna Boyd5E2C]

Everyday, I take mobile screenshots and put them in a phone "shell".  It's an easy replacement, and seems ideal to have some sort of automation where the screenshots are loaded into one folder, the application grabs them and spits them out in a finished folder.

Unfortunately, my photoshop skills are on the beginner level - I've spent hours trying to find a solution o n this problem and have had no luck.