It's just a "common problem"
Well if you change the intrument binnacle you're going to have problems with your keys/alarm cos if I remember rightly part of the system, particularly the coding, was built into the dash...
I know with the older 80's and a4's the computer bit in the middle was an added piece which could be fitted into the dash but then there's the wiring loom to change and maybe some of the sensors... If you're seriously thinking of doing this it might be worth grabbing a copy of elsawin off fleabay and do some research.
Hope this helps.