On Mon, 8 Jul 2019 07:27:25 -0700 (PDT), "
wrote:

The MOSFet will set you back a princely $4, including shipping.
The cap will set you back, perhaps, a whole dollar ($1).
The controller - perhaps one more whole dollar ($1).

One of the goals with this repair attempt is to learn something about
SMPS. So, before I start throwing parts at it, I want to scratch my
head a little and try to go the methodical route.

Replace them all. But only *after* you have checked any and all diodes for open or short conditions.

OK, I will check the diodes.