Sounds like a real quality product =)
Most (any that I've heard of) LCD failure modes simply result in the display ceasing to function. Then again it depends on of the LCD is a module or just a simple display. If it's a module the driver is on the board with the LCD which means putting it in the non-functioning LCD's unit will result in the same dim display. If it's truly just an LCD unit with connections to a driver board inside the unit then swapping out the display may work, unless it's really a faulty display driver problem in which case you're pretty much out of luck. If it's not too difficult try swapping them.