Hard drive help

Hi all
A friend of mine has some DL:2's that are in a bit of a state
basically someone came to 'fix' the hard drives and started to replace them however now he is left with them all not working
I am stepping in to try and get them going but have very little knowledge of the internal workings
Basically I want to start with blank hard drives and install them from fresh
if someone could give me a step by step it would be much appreciated
Thanks
Mikey