FYI: For future reference or search
VAG Auto 'boxes are not the best in the world, to be honest. They were a joint effort with Renault.
Yes, you can drain and refill. Buy the OE fluid from VW/Audi. You'll need about a gallon. There should be a drain bung underneath. IIRC the diff oil is conventional oil and seperated from the transmission unit itself so needs changing seperately.
There is no filter as such, there is a pick up strainer inside the sump. If you want to change it you will have to remove the sump. You'll need a new gasket when you refit it. I don't think there is a change interval on these - they are a sort of 'last resort' to stop swarf circulating.