Turns out they had no videos for replacing the transfo, and neither did anyone else. So I winged it. Not too complex, just that you're up on ladders working inside a box with room for an 8 y.o.'s hands. removed both side covers, unclipped the lights, removed the circuit board, unclipped the old transfo - had to cut some tiny ty-wraps, unscrewed the transfo (suspended in the box, to make things simple) and restart in opposite order with the new transformer.
Took about an hour and it now works as good as new!