, you should back it up before swapping it juuuuuust in case something bad happens.
Remove the screws, feet, or screwfeet then follow the instructions in the case to install the drive and build the case.
I recently linked to a Macally case that's USB 2 & FW400. Unfortunately the only other Firewire cases I've found are at OWC. Between the lack of Firewire ports on new systems and Apples wholesale adoption of USB-C connectors it seems to have led case manufacturers to discontinue older cases, even if they were ones that included USB 3 ports.
I'm a biiiggggg fan of screwfeet . . . always have been, always will be . . . in the olde "two birds" sense of technology.
And, thanks for the details . . . the infinite number of switches would indeed be daunting. And, just to show how far I've fallen behind the wave, haven't even heard of USB-C . . . but, the MPro has USB-2 & 3 ports, the 3 is significantly faster . . . .
And, yep, from memory it looks like the Fantom case is pressed or snapped together . . . it was "reasonable" as things have been pretty "tight" . . . should have gone for something more quality . . . but, since it was the "back-up" for a couple of computers, and there was no warning of impending doom . . . "accessing" it and trying to back it up???? Is that possible to do if there is no power to the drive??
Also from what you are saying, it might in fact be better to use the computer shop, if they have an old case sitting around, it might be exactly from the time zone I would want . . . firewire, etc . . . ??? I'll have to look around and see what shows up; perhaps this might be something that eBay would suffice to provide????