Yes, I once gave as well the computer for some reparation and actually, it was just the power supply that went on holidays. For good.
I changed it and they even not charged me for the "opening" of the laptop as they found out immediately the origin of the lack of power.
BUT, yes. Usually in the computer we all have something quite compromising and it would be good (like we always say) to have a separate back-up for such data
I worry about security a lot these days, but I am not sure how safe anything ends up being. It is a very real fear for me after all of this work.