IF there is a gear box repair u should be in the place till the work is done . we can't trust people.
try below places
1st step Mr Nishantha ( 0777799953) he is an electrician.but gear box activities are done.he is a honest person. so talk to him and get an advice.
in some places gearbox repairs are done.(use google to get information about them)
Rasanjana motors( he was a clever man when he was young but not now)
Nilwala motors( be careful he chargers a lot but good)
Nilanka gear box repairs(he gives 100000km or 1 year warranty) but chargers are vary from person to person)