Bluetooth is not the most difficult retrofit; I have done it to my 2005.
You will need:
1 Microphone (drivers side of roof console, plugs in under roof console)
2 Phone module (behind nearside boot lining)
3 Additional D2B (optical) harness (if you do not already have a D2B device in the boot you may not need this)
4 Voice bypass jumper
5 BTUM (actual bluetooth unit; under centre console; your year should have the correct wiring; mine didn't)
6 You will likely need to 'code' your car to get everything working (especially if you do not already have a D2B device in your boot)
You can fit an X-Type combined PSE and BTUM (7w93-10d893-ab) in place of items 2 & 5 above; this will need a bluetooth antenna (this is what I fitted).
With the exception of making a hole in your headlining beside the roof console, and the 'coding', it's all plug and play.
Cheers,
Aidan
PS: my car details on this forum are out of date; I have both a 2000 and a 2005 S-Type