One complication with mine was a problem with the thread on the end of the driveshaft (I assume this was due to the original assembly or a previous repair), which meant that had to be replaced too. I understand there was a bit of a fight between Alfa Romeo, who were shipping parts from Italy because their UK warehouse had lost track of their inventory and the warranty company, with my dealer (Monza Sport) stuck in the middle.
The good news:
1. they kept me on the road with courtesy and rental cars for a fortnight.
2. it didn't cost me anything and, apart from the time taken to exchange a couple of loan cars, I didn't get involved in any of the hassle.
3. the car goes like a dream now ...
I wouldn't expect anything less from the 4th year warranty.