subvinorosa, opening an external drive is not scary. It's just an internal hard drive (hdd) inside an enclosure. Allowing him to "take it out" should not damage the integrity of the drive in anyway but will allow him to connect to the hdd in other ways (connect it internally to another computer, use an hdd dock, use another enclosure).
I had an external drive die on me once and it turned out just to be the enclosure. The actual hard drive was fine when I removed it from the enclosure and used another.