Ive just been doing this today so its fresh in my mind.
First remove the panel in the centre of the dashboard top, this contains the alarm led and I belive a temp sensor again looks like a led.
This is just clipped on I used my Jaguar Keyring to prise it up.
When this is out looking at the reflection in the windscreen you will see the trims containing the tweeters are fixed under the panel we have just removed with a philips screw, normally no problem but in this case its just behind the windscreen.
I used a small spanner and a philips screw bit to remove the screw, the trim will then unclip but beware the end with the tweeter is fixed with a plastic stud and this will stay in place.
The tweeter is a twist fit on a baonet type fitting and the cables are fixed with a small tight multi conector, before I fitted the new tweeter I tested it first (always a good idead)
Nows the time to remove the plastic stud that more than likley will still be stuck in the dash top and fit this where it should be in the end of the tweeter trim before refitting, refiiting is just a push fit followed by the one philips screwbut make sure the trims are lined up right or else the centre panel wont fit.
Job takes 30mins at the most and yes it sounds so much better.