Help With Gdvr9

Well sort of, My cousin who has the local shop to me has an .......AV-TECH GDVR9 9 CHANNEL DVR W/O means nothing to me but he says that the hard drive is busted and he needs a new one installed, He has approached a few repair ppl and all they seem to want to do is sell him a new system. I asked him if he had the manual so that I could get a little more information but at this time he hasnt brought it round, so questions are can a new hard drive be easily installed if so what kind is there any software that has to be pre loaded onto it and could I do this from a pc and is there anywhere I can get hold of a manual so I know what im dealing with.............. ken