It's at the top of this forum at;threadListing

If we must save files before we send it in, we pull the HDD and put it on some cable like this one.

Why not retrieve your files before the machine leaves your hands? That is, part of the repair system usually installs the factory image.

About what's failed, today's makers rarely tell what happened as this is an added cost to the repair so to keep repair costs low, it's run through the repair group which has, as a mandate to keep the costs low. I would not count on any details of what was done.