Every time a user selects a different item int the top-left combo box, the rest of the GUI in this tab needs to be updated to reflect the entry in the item data table for that item. What should I google to learn more about this?
If I understood this right, it's a matter of creating an event for the top-left combo box (most probably actionPerformed) in which you send messages to all the objects you want to be affected (setSelected = true for example).
How you decide what to assign to each object will depend on how you're storing the data of each item ID, of course.
I think I'll have a dictionary/map that where the key is the item name (a string) and the value another dictionary/map that is all of the bytes for that item's entry in the item data table. That way when I need to read from it, I input the item name and then the index of the byte I want to get, and I have a bunch of switch case statements and whatnot for updating the gui elements that represent the state of that item's entry. When I want to write to it it's the same, except when I'm only writing a single bit in which case I need to do a bit of math.
This sounds like only one dictionary/map to me. The key would be the item name / number and the value would be the byte array (or even just an int or a long, if you store the data as bits).
Does this sound sane? I could also do it with an array (or an array of arrays) but I want to do it in the easiest possible way to maintain and focus on performance once I have all the features I want.
I would advise to get rid of the bunch of switch-case statements. Most of your options are radiobuttons, which only need a 0 or 1 value you can get via bitwise operations.
I would also recommend finishing the GUI before going into functionality. Most GUI editors for Java are a bit of a bitch if you decide to change something later.