Follow Franklinstein's advice, and you're likely to get at least two of them working. The grease tends to turn gooey over time, and that's what commonly causes the heads not to load properly, or the disk auto-insert to fail. Just clean off all the old grease, and then re-lube.

On the first drive with the head loading problem, see if the head assembly is actually mangled. I've seen this on a couple of drives, probably caused by overly aggressive attempts to pull out a stuck disk. If that's not the problem, then your chances of repair go up markedly.