I upgraded my 2008 XF Premium Luxury to the top of the range Bowers and Wilkins setup.
I was lucky enough to have a donor car so the transplant was relatively painless. The head unit does need to be changed to the multi disk version,
All the wiring was pre-installed with the exception of the centre dashboard speaker and it was no biggie to lay in a loom for that,
IIRC, it took 2 hours from start to finish, plus 20 minutes programming with SDD.
Overall, the B & W was well worth the time effort and cost. As far as cost was concerned, the breaker who had to donor car asked for £50 and I could take whatever I wanted.