Hi mr scotty
A mercedes c200 from 2008 with automatic gear box and 130 000 kms. The gear oil has never been changed .the mechanic told i need to flush the entire quantity of oil and put a new one (about 7 liters) do u think if i do this process it will break the gear box?

it might, I would change fluid but not flush. And ONLY use Merc fluid

Do it at least 2x, drain and replace within a month, no flush