Its three gaskets, and Nissan doesn't do turbo gasket sets anymore, so you just order in the three.
Before you do though, better to check that's what is actually causing the problem. The recommendation I have seen lately is to mix up some detergent with water and put it in a spray bottle. Spray all the possible connections, fiddle with the throttle to rev it a bit, and look for the bubbles.
Hard to say if it will cause any damage without knowing exactly what/where it is. At a guess, probably not, but it will throw the mixtures out as air is escaping.
LW.