JustLooking

Ok Hi everyone..it's my 1st time here....
My pc crashed last week, the blue screen and everything. It happened once before and a friend of a friend fixed it for me without losing any of my data. I asked him to do the same this time, and he took the pc to his work place and tried to fix it, it turned out the harddrive i guess was really damaged and he couldnt save my data, but he said he fixed it to work properly. I'm getting my pc back today, but now i am totally freaking out because it crossed my mind that he could have maybe accessed my files, the important ones were hidden but not in any special place. He said he fixed it to work alright, but he didnt say weather he replaced my harddrive with a new one or just cleaned my damaged one. If he replaced it with a new one, I'll ask for the old damaged one back, so that i can destroy it, all of my files on it, even if they aren't accessible anymore. I'm just wondering how can i know that it is my harddrive he'll give back, the one i had, and how can i know if he by any chance was able to access my files and copy any of them? I dont know him personally so i cant say what he would or wouldnt do, but i'm really worried :( Help me please if you know a way i could know my data isn't exposed.