DSG oil and filter should be every 40k, priced £179 at VW now.
As above, would not do anything until you have it scanned, often the dsg box reset can cure faults.
It may not be the mechatronics unit, but think others have had an issue with the selector/shifter unit (apologise if i have this term wrong).
So you have an idea on price my mechatronics unit was changed 12mths ago under warranty and it was approx £1,850.