I think your mechanic is talking cock and bull story, especially the "Engine comes from Indonesia".
Hello mechanic~! Engine is Mitsubishi and buatan Malaysia only la~!

Secondly it's possible.Just need to tap from the ECU, or crank sensor, depending on the car.
Goto another (any) accessory shop and tell them you want to install RPM meter.

Read this forum: http://forum.lowyat.net/index.php?showtopic=400189

But it's preferably to install WIRA 1.5L or Mitsubishi (imported) meters, cause they are the most accurate.

I have tried before, comparing the AutoGauge and a "swap over" Nissan Sunny "EXTRA" model meter. The ori Sunny meter is more accurate than the AutoGauge.