E65/E66 Buying advice.

[lambo_xx]

A friend is after one so I said I’d ask on here. Budget would be between £6-9K for the car. I said go for the V8 but apparently has to be the diesel.
Questions are what to look for? Anything specific on these?
Spec wise, any must haves?
What is real life economy like?
BMW offer a warranty, is it worth having? Or will it be such minimal cover on a car of this age it isn’t worth having?
He currently has a 2007 318D. Will running costs be much more?
Lastly, is there any way of getting an ipod connection in the car?

Thanks for any help! Really appreciate it!