There is of course a totally different way to achieve exactly what I am trying to do, without re-initializing the wavetable, and dealing with having to wait for sound to stop, or stop it myself.
As it is an array, I could just always upon app startup set it to the highest size, and then use an adjustable (via slider) step variable to change the oscillator resolution. That way I should even be able to adjust it while the sound is playing!
Problem is that I do not understand the tutorial code enough, as to figure out where to insert such a step variable.