are you blowing blue is smoke? have you checked the PCV's? do you have a catch can? you might want to get an endoscope or some other type of camera up under there to see exactly where this leak is coming from. my guess would be cam cover seals or oil feed pipe to turbo.
yeah, again both crap to do but a hell of a lot easier than pulling turbos.
and yes as far as I know you can do them with the engine in BUT if you have complications it will be a NIGHTMARE !!