Other than using non-abrasive LCD display cleaners, there isn't anything you can do to recondition the display itself.
There's not much you can do for other damage either. If anything has taken a hit that is enough to dent the unit, there's a chance that other sensitive components inside the unit have been damaged. Other "fixes" and modifications can have non-obvious consequences. For example, customers that have filed parts of the EFIS-D10A/D100 bezels down to allow a tight fit have ended up getting metal shavings inside the unit, where they short out electronic components.
Anyway, give tech support a call at 425-402-0433 if you want to discuss your unit's condition more specifically. We may be able to help.