Yes, I just wrote my sentence in a wrong way.
I'm not willing to try to replace just the gorilla glass: even if the glass of my phone is cracked and the lcd is still ok and actually I'm still using the phone anyway, I'm following with a lot of interest this discussion to try to have a feedback from the users who have already bought the complete lcd part in order to buy one for my phone as well.

Despite that, it seems that some sellers are also offering just the N9 glass for around 10$, even on ebay, and on youtube there are a lot of videos showing people replacing just the gorilla glass on iphones and other phones. Apparently it seems that the glass has to be completely cracked and removed first, and that looks like a very tedious and aggressive job even if they say that the process is easier after warming the glue film (silicone?) between the lcd and the glass with an hairdryer.
Even in case that this would be possible, replacing the whole part sounds definitely much more convenient to me