I know a watchsmith near Paya Lebar. I have been there a few times for repair, service and movement swaps. However, the charge is fixed at $150 for any service, whether it's repair, tuning, servicing, or movement swap. I'm not sure if this is too expensive. If you're interested, you can PM me, but please note that my last visit was 2-3 years ago, so I'm not sure if he is still in business. If anyone wants to try their luck, let me know.