i tink NSC would be the best place..... they should be the expert. especially if its still under warranty.
else, maybe you can try TCW(the camera workshop) next to funan the hotel. i think there is a sticky somewhere with the address. its right next to the NUG gathering place
my fren did a sticky aperture blade repair there b4.. not bad...
Always check the price with the local service centre against the shops in Adelphi or Penisular first. The last time I checked personally for my Canon lens, it was actually cheaper doing it at Canon Service centre than at these smaller shops.