Someone needs to write an LED buying book for Holly35. :) As far as the crystal being plastic or glass, ask the seller. If it makes a distinct clink noise when you flick your finger on it, it's glass. As for what's inside these things, it's a crap shoot. I've had some Waltham watches that had terrible modules in them...The non working kind. However, somtimes companies like Waltham would source better modules for certain watches.
Good luck...
Jeff