clunking noise when shifting gear and turning corner

Hello everybody

I am facing this issue while changing gears and turning corners, I can hear a clunking noise like that of metal parts hitting each other, this happens at times when I am changing gears, sometimes when I am turning corners I can hear this kind of noise. 

I spoke to the authorized showroom guys, they suggested the gear oil has to be changed and gear shift boot would have to be replaced and the overall cost would be around 7000 rupees. 
I do press the clutch fully while changing gear, inspite of that I am facing this issue.
and should I take the vehicle to the authorized service only or a local mechanic could sort this issue out.
Any assistance in this regard will be aprreciated

It sounds to me that the front wheel Bearing is shot ! does it go Clack Clack Clack when you pull away with a full lock ! ? Check the rubber boot on the end of each drive shaft