Paranoid jewelry store will swap the diamond in my engagement ring when I get it resized?

I've been putting off getting my ring resized since I got it 6 months ago and am taking it to get resized today. I've had a coworker tell me when she did that with hers they swapped out the diamond with a fake. Should I be worried about that happening with me? How can I know if I get the same diamond back? Will I look stupid if I ask to look at it under a microscope when I drop it off, and again when I pick it up?