Assuming you're talking about the gas turbo (as opposed to the diesel). Not sure if it makes a difference regarding your question but they do have different turbos.
From what I've read here the gas turbo bearings are lubricated with engine oil and cooled by a line from the coolant system. I don't claim to be a mechanic but surely those lines would have to be disconnected in order to R&R the turbo which could introduce air in the line.