It took my brother around 3-4 hours to fit the Alpine kit in his E90 and he commented on how easy it was to do, the upgrade is worth it though as it sounds amazing.
Definitely something a novice can do as long as you have the correct tools.
I have a Pioneer 3200bt unit in my Alpina and the parrot system work with that perfectly.
Alpina D5 bought 2015
Alpina D3 sold 2015