Hi @Jason_Nutt,
Excellent to see your learning progress! If you do get stumped while taking MongoDB University courses, definitely ask for assistance in the dedicated course forums (eg https://mongodb.prakticum-team.ru/community/forums/c/university/m121/67). There is a MongoDB squad that supports learners in University courses (coincidentally, they are now part of my Community team!) and many helpful community members.
I also recommend using the Aggregation Pipeline Builder in MongoDB Compass to develop and test your aggregation queries. Since the output of one pipeline stage is the input for the next stage, complex aggregation queries are more straightforward to troubleshoot if you work on adding one stage at a time.
You can use a similar technique in the MongoDB shell with variables (for example, https://mongodb.prakticum-team.ru/community/forums/t/mongoerror-a-pipeline-stage-specification-object-must-contain-exactly-one-field/120870/15?u=stennie), but Compass provides a visual reference with some sample documents.
Regards,
Stennie