It needs doing at 40K, I know this from recent conversations with Seat Dealer. They also said it doesn't need to be done before 40K... it doesn't get very hot so doesn't thin etc.
From very recent experience I know its quite a big job though
Took mine in for inspection as was getting strange noises and general lumpyness with the DSG local dealer said I needed to prove the oil had been changed at 40k (The car was serviced at 38K just before I bought it and I had no real way of proving if it had or hadn't)
Long and short of the story is that I was sold car with full service history which it didn't seem to have (everything else was in order but this gearbox oil change hadn't been done)
Dealership I purchased from have today replaced oil and filter and its a completely different driving experience now. Although they did have the car from 8 this morning til 4.
So far no strange noises though so I think the oil change has solved the
problem, fingers crossed..
In your situation I would be ensuring the dealer changes it FOC if they think this will solve the
problem. If the book says 40K then thats what it should be...