For the file not showing up and corrupted, i suggest that you do a full low level format on your player using either the MP3 Utilities Disk Tool (that came with your player) or use the HP Format Tool (downloadable from the downloads section). There is a high possibility that your player's memory might be hacked and causing you all the file errors.
As for the ipod screen changes, you will need to extract your current firmware and repair it, the guide is
HERE.
Next, using the S1res tool (from the downloads section) to edit the repaired file to your liking. Editting guide is
HERE.
You can find a wide variety of themes which can be used in the downloads section too.