Pate de noisette is just hazelnut paste with some sugar added. Technically, praline is made from either carmelized almonds and/or hazelnuts. Nutella is pretty much the same thing as pate de noisette, but I believe it has a higher sugar content. However, I'm not positive. In any case, you should be able to substitute it with no problems.
I made both pate de noisette and praline noisette. I used praline noisette - milk chocolate (2:1) . I think pate de noisette needs dark chocolate however. If i try to make it like nutella can any one tell me how much cocoa(ratio to praline noisette) should i use? Thank you!