SCSI CD-ROMs are hard to get (probraly only used) expensive and require an extra controller either as a seperate card or on a CPU-card. If you have neither of those getting a longer IDE-cable should be much easier. Just check random shops selling anything computer.
On the SW side you should be able to get away with useing just what supplied with AmigaOS (not sure wether OS3.0 has everything onboard, but 3.5 or 3.9 should be sufficient).
