This was one of the points drilled into our head the last time I did a new job orientation (15 years ago): Your computer is warranted by Dell, they will usually send parts directly to you, sometimes they will send a tech out and it's your responsibility to watch him, if you have to send it to the depot remove the disk.

I am surprised that the OP did depot service for keyboard and trackpad. I replaced my own keyboard twice and trackpad once (trackpad was actually part of the housing.) Maybe my enterprise had a special agreement with Dell to let us do this?