How do I correctly classify retail fixtures such as slot walls, sales counter, hangers, etc? Are these assets or are these expenses? How about the labor associated with installing these items?

If you classify them as assets, then the labour too would be added to the cost of the asset.

If you classify them as expenses, then the labour will also be an expense.

How to classify them? It all depends on materiality.

Do these items have material worth? If yes, then capitalize it (make it an asset), if not, expense it.

Hangers, etc. don't sound like would have a huge materialistic in your business, so I would expense it, but you need to look at each item and make a case by case decision.