@digiteye:
Your are not totally correct my friend, the VW 170HP diesel engine has different injection valves and also some other stuff changed...
The 3.0SD has bigger brakes, improved cooling and a back axle differential that can take more torque. If you have the extended trailer weight option (SA233) you also get this features BTW... the gear box might be the same, i´t has the identical type code as the 3.0D and the 4,8i.

Warranty: Any car manufacturer will state that the warranty is void when you an aftermarket tuner will pimp the ride...
Of course if it´s standard by BMW or VW you have full warranty

Have a nice weekend

Christian