New Hard drive, no original disk to reinstall operating system

I had a black mac book and the hard drive stopped working, got the grey screen with a flashing folder question mark, which i heard was a common problem with the black macbooks specifically that are about 3 years old. I'm in china right now so i couldn't go and get it fixed for free, so i got a new hard drive installed, but i don't have my original disks that came with the computer to reinstall the operating system. The shop installed a pirated version but they say it'll only work now while the disk is in the computer, and that if i buy new authentic software it'll be the same case, do i have to get my original software mailed from home or is there a way around this?
much appreciated

thank you for your help, i'll buy a new os, also, they installed a hitachi hard drive, is this a problem, does your internal hard drive have to be apple?