it will be ok after you leave the underdark. the only items that will disintegrate on leaving the UD are real drow items -- i think they all have a warning in the description, and all are purple colored, as far as i know. most everything else (the stuff that you buy including potions and armor) will remain intact.
There's a very nice set of armour (Gorgon Plate ?) which can be used above ground - you can loot it from one of the bodies after the demon's appearance.
Neither Saving Grace +3 nor Gorgon Plate +3 is a drow equipment. No need to worry.
Note: you can buy Sentinel +4 medium shield in the Drow City. Sentinel is not a drow equipment, either.
