Hey Cimeto,
Thanks for the helpful tips so far, I'll look into using Lists instead of Arrays. After posting the question, I've worked on it a little bit and noticed that I should've declared a separate class for Inventory, and use a List<Item> to represent it as you pointed out. I looked up the Contains method for the List data structure and it seems like it has the Contains() method I needed the entire time. Whoa, what's that set and get thing, I learned about that yet. Does that automatically act as my getter and setter methods in C#? So, the auto-properties you were talking about are essentially values that are automatically assigned to empty fields right?
Thanks for the help so far :)