Am I correct here in assuming that one CAN (simply) replace their original
bootable HD, without reinstalling Windows and all the programs all over
again, by either using Ghost, or (maybe?) the HD manufacturer's utilities
that come with the new drive? (I'm thinking of Western Digital here)

Do the drives have to be the same size for Ghost imaging? Hopefully
not!!!

The more I think about this, I think it would have to be done with Ghost, or
something like that, to prevent reinstalling everything all over again. I
doubt if the HD manufacturer's utilities would be enough.