I used to work MX @ TCM, awhile back. I believe what you're talking about are the QAR tapes, which were located in the smaller avionics compartment right below the bunks - you face it in the left CRACM seat. It's a tape, some sort of DAT or the like, so no PMA involved. The C-17 doesn't use PMAs aside from Panasonic Toughbooks used for electronic TOs (called the D-TOS), which is really just like the normal e-pubs. Nothing magical about it, just a tougher than normal laptop. It still breaks when someone, say, lets it fall when working up on the wing. Yeah that happened.
I remember changing out the tapes and handing them in but don't remember who necessarily, and I think it might have been a Mx Specialist job (like Com/Nav or GAAC or something) that I did to help out with.
I also didn't work with anything more advanced than the Block 15, McChord had just gotten its first COSA jets as I left maintenance. So it's possible it's something else now.