Theres an ISOT novel, The Other Time by Mack Reynolds and Dean Ing that basically goes there. While a timeshifted archeologist is an 'easier' catalyst, it's only borderline asb that the Aztecs could pull a similar trick on their own.
It's certainly easy to get Cortez defeated, and, since his expedition was unauthorized, the Aztecs would have had breathing room to try new techniques. Assuming they spared some of the more skilled soldiers, introducing wheeled vehicles and iron, probably even steel isnt a total stretch. And, yes, theyd probably need a blacksmith to teach them.
Sure, theyll be technologically far, far behind the Spanish, but even with the massive pandemics coming, they out number them massively. Whether they can hold out in the long run is an interesting question, but at worst they should be able to get the kind of status British India had, governed and oppressed from afar, but native structures largely staying intact, rather than otls total Spanish takeover.