What is the best way to clean the clear plastic lenses over the guages? I know they scratch very easily, and want to know the best way to get them clean without scratching them. Thanks!

Dust them first, then use a soft rag and non-streak cleaner.

If they are a bit scratched, you can polish them with Meguiar's Plastic Polish.

I hit it with one of those air cans for cleaning electronics, to get the dust off, then I use disposable wipes that I have for my glasses. They make a pretty same thing for pc monitors.