So I tried this:

$ sudo modprobe md

...and it just sorta did it. If I understand the man pages correctly, I'm basically telling the kernel "Prepare for a Software RAID." Yes?

$ sudo mdadm --assemble --auto=yes /dev/md0 /dev/hde1 /dev/hdf1 /dev/hdg1 /dev/hdh1

Did this, and it says:

mdadm: device 3 in /dev/md0 has wrong state in superbock, but /dev/hdh1 seems ok
mdadm: failed to RUN_ARRAY /dev/md0: Input/output error

...and, in the interests of not getting in deeper than I can handle, I calmly, humbly and appreciatively await further advice.

Thanks, greenfly!