newbie here so sorry if this has been covered , but i,m looking to fit a symphony 2 double din headunit into my a4 b7 ,it has a single din headunit fitted, i,ve managed to get double din headunit and i know i have to trim the climate control unit but what else do i need and where is the best place to get the parts ,i,ve read i need to change the single din cage to a double din ? also read i have to change ashtray ? i,ve read a lot of post s guys but a lot of the links seem to be inactive thanks