It's a better system than the standard setup. There is no wiring fitted in any VAG car for any non-factory fitted feature.
In a non Bose system the speaker wiring goes to the head unit, on a Bose system it goes to the amp in the boot. You'll need a compatible head unit and you'll need the MOST cables from head unit to the Bose DSP/Amp. you'll have to take the door cards/rear door/rear quarter cards off, to change the existing speakers and fitted the additional ones (rear seats have to come out to get some of the trim off).
Once done you'll need someone with VCP to modify the head unit and code. The coding can be done with VCDS but not the re-paramterisation.
If you have to ask how hard then I wouldn't even attempt it tbh. Upgrading to the Audi Sound System is relatively easy in comparison but you still need door cards off and have to add wiring for the centre speaker and subwoofer and modify the head unit if it supports A.S.S (I've done this on mine).
Hope that helps?
