Nah didn't do a guide for elbow but it's pretty straight forward.
If you haven't already take off the manifold heat shield etc first. Then there's access to top of elbow from engine bay. There should be x3 bolts where the elbow flange meets the turbo exit flange. Loosen these. Then go under the car and undo the three bolts/nuts that connect the elbow to downpipe. Once the downpipe is out of the way then you should be able to take off the two bolts on the underside of the elbow where it meets the turbo housing. So there's x5 nuts in total that need to be taken off to remove the elbow.
Lamda sensor is removed obviously from the engine bay above...
I would seriously WD40 every nut and bolt plus lamda nut you are removing the night before. Lots!!!
Deffo get your turbo to elbow gasket from Nissan. You might also want a gasket that goes between your new elbow and the downpipe (Conceptua Tuning sell these... don't need Nissan circular style). Lamda (O2) sensor I'm not sure if Nissan's the best place? Probs expensive!! :wack: