Hi Moto,
From my experience, I would suggest caution with second hand drives, as they can appear to be fine at first, but have reliability issues down the track. I've had a couple of bad experiences with second hand drives, and try to avoid them as much as possible. There's nothing quite so fun as pinning down an intermittent problem, spending lots of time troubleshooting, and possibly loosing valued data. If you can afford a new drive, and get an adapter for it to connect to your miggy, that may be worthwhile. If you need an old drive, some shops may sell with a limited warranty.
Also, I would always recommend reading thoroughly about a product before buying. There are some very good guides to SCSI hardware online. It would probably be worth reading one or two of these.
Good luck,
Oli
