It's a pretty good concept, but I think it could be done much better.
For instance, the user shouldn't have to interact so much for the loading. I should be able to select my iPod and have it automatically extract the firmware, back it up to my ~/Library/Application Support/. When it extracts the firmware, it should also read all the resources simultaneously (also out of sight). Having the user do this interaction is not very friendly. If they're going to be working with the same firmware file (or its extracted resources), why have them manually select it for each operation?
The same goes for saving it to the iPod. I think an "upload" button would be in order, which would just save all of your changes to a new firmware file, then send it to the iPod. If you want to restore from a backup, it ought to just present you with a list of them (which are stored in ~/Library/, remember?) with dates and let you select them.
I think a search feature for strings would be a good idea. There are hundreds (thousands?) of them to sort through. Also, I don't think it's a very big deal if one is empty, so it shouldn't display an obnoxious sheet window every time one happens to be.
What does "Preparation" do? There's no documentation for this. I say get rid of it completely, it's very confusing.
Although the firmware file is 32 MB, it compresses down to a mere 3 MB with the Finder's built in zipping capabilities. This would be a good way to store backups.
Also, please check your spelling and grammar. I swear I saw a "No iPod's detected." somewhere in there.