The other day my car was working fine, Then it wasn't.

The engine started, the first thing I noticed was that the A/C wasn't working. Then when I moved it into gear, it moved just a few meters, then stopped. PRNDS on the display started flashing, and the car refused to engage any gear.
An engineer from the dealership came with the computer thingy, took some diagnostics and came again the next day. He said that he needed to send the diagnostics to Germany to find out what is wrong.
Today they phoned me and said that the DSG gearbox has to be replaced! They were unable to explain to me what exactly is wrong with my car. They were also unable to explain to me what is the mysterious connection between the gearbox and the A/C.
I'm hoping someone can help me here, since I have a feeling that some minor electrical problem is being mis-diagnosed.
My car hasn't been chipped or modified, it's been treated well, and it's only got 18000 km on the clock.