It's taken a while but I've tested out the procedure and it takes about 10 minutes to replace the controller. Our spare ones have the same ONTAP and firmware version and we swap the whole controller (flash card included).
Thanks for the reply - the "motherboard" we've been quoted on (X3244A-R5) is listed as a spare part for the 2040 and I don't see "controller" listed so I'm hoping they're the same. I'll confirm this before ordering.
Thanks for the steps too. As the 2040 isn't in production use yet, I'm hoping I can swap the controllers and configure the standby one. Then in an emergency we can just swap the failed one as per your steps (provided the firmware hasn't changed).
I'm hoping that pre-configuring the replacement controller would mean that downtime is very short. Any comments on this approach?