ORIGINAL: rlipsett
try some novus plastic cleaner. the stuff is midly abrasive and will polish up plastic and make scratched plastic clear again. I use it all the time on my pinball machine plastics.
Another vote for Novus plastic polish. It is what I use to clean the plastipane panels on the dodger of our sailboat. Also works on canopies of r/c models. Flitz might work, too.
But first, do we have a definition of what "screwed up" means in reference to a transmitter display? Scratched? Dissolved? Blackened? Moisture behind the cover?