I decided that the better part of valor involved replacing the failed hard drive sooner rather than several days later, so I went on line, found the drive at a local Office Depot, ordered it, and picked it up this morning. The replacement is now installed and the mirror is rebuilding itself, which makes me feel better.
The drive that's coming from NewEgg can be a spare. :)
And the fan is still very necessary. I had to spin the old fan up by hand to get it started.