Hey Jon!
Is there one? One planned?
This one is on me :) Yes, there has been one in preparation for quite a while now, but I have not managed to complete it by now, both content- and presentation-wise, I am afraid.
I understand that this is a major entry barrier. Mea culpa. For now, the best I can offer is a cross-reading exercise:
Gustaf Neumann's migration guide maps XOTcl concepts to NX concepts. So by reading up basics on XOTcl (ie manual and tutorial at http://media.wu.ac.at/doc/index.html), you can then jump to the "closest" NX equivalents by following the migration guide at: http://next-scripting.org/docs/2.0b3/doc/nx/nx-migration/index1
//stefan